Methods for residue removal and corrosion prevention in a post-metal etch process
A method of plasma assisted CO 2 cleaning for dry removal of residual photoresist and sidewall polymer with an etch gas mixture comprising fluorine containing gas, oxygen and hydrogen in N 2 or H 2 O. The process removes polymer residues present on a metal layer on a substrate and on the sidewalls of metal lines and inhibits chlorine-based corrosion while being very selective to exposed Ti, TiN, Al and SiO 2 . The invention is particularly suited for removing post metal etch polymer residue from top and sidewall of metal lines.
1. A method for removing residue materials containing a polymer in a post metal etch process, comprising the steps of:
introducing a substrate having a patterned etched metal layer into a plasma chamber;
generating plasma from a gas comprising one or more fluorine compound containing etching gases at a temperature of from about 25 degrees C. to about 80 degrees C. and at a pressure of about 0.5 Torr to 10 Torr or less, for a time period of about 30 seconds, wherein at least a first portion of the residue is converted to volatile species and removed via pumping, wherein at least a second portion of the residue is converted to compounds that are soluble in CO 2 ; and
exposing the substrate to a flow that contains CO 2 snow for a time period of about 10 seconds.
2. The method of claim 1 , wherein the second portion of the residue is converted to fluorinated species that are soluble in CO 2 .
3. The method of claim 1 , alternatively, in claim 1 a CO 2 treatment is done first where chlorine-containing residue is soluble in CO 2 .
4. The method of claim 1 , wherein the CO 2 and plasma processing are performed simultaneously in a single step for a period of about 40 seconds.
5. The method of claim 1 , wherein a pressure during the CO 2 treatment is between 10 Torr and 20 Torr.
6. The method of claim 1 , wherein a pressure during plasma treatment is between 0.5 Torr and 10 Torr.
7. The method of claim 6 , wherein a substrate temperature during the plasma treatment is between 25–80 degrees C.
8. The method of claim 1 , wherein the metal layer is an aluminum-containing layer.
9. The method of claim 1 , wherein the step of generating plasma from a gas comprising one or more fluorine compound containing etching gases is performed with a fluorine containing gas selected from the group consisting of CF4, C2F6, C4F8, CHF3, NF3 and SF6.