AVS 45th International Symposium
    Manufacturing Science and Technology Group Wednesday Sessions
       Session MS-WeM

Paper MS-WeM1
Complete Solvent Free Stripping of via Structures using NF@sub 3@,H@sub 2@O,O@sub 2@ Ashing Chemistry

Wednesday, November 4, 1998, 8:20 am, Room 317

Session: Advanced Process Equipment and ES&H
Presenter: W. Au, VLSI Technology, Inc.
Authors: W. Au, VLSI Technology, Inc.
R. Solis, VLSI Technology, Inc.
R. Bersin, Ulvac Technologies, Inc.
H. Xu, Ulvac Technologies, Inc.
M. Boumerzoug, Ulvac Technologies, Inc.
Correspondent: Click to Email
The use of TiN as a base material in submicron vias employing tungsten plugs is becoming more and more accepted. One difficulty, however, is the etching of these vias and subsequent removal of polymeric residues residing at the via base and along the vertical sidewalls. Removal of these residues prior to deposition of a Ti/TiN glue layer is most critically important to achieve low contact resistance in the vias. Resist stripping and polymer-residue-removal from submicron vias is an area of intense interest at this time. Methods employing fluorine-based plasmas to render any residues DI water soluble, thereby avoiding costly and corrosive solvent processes, are under serious investigation. In this instance of TiN based vias, however, undercutting of the TiN and resulting high via resistance have been a major obstacle. A new process has been developed which address this problem. The residues are ashed utilizing a low bias RIE plasma comprising oxygen, NF@sub 3@, and H@sub 2@O vapor in correct proportions. The presence of the fluorine renders any ash residues soluble in DI water; and the H@sub 2@O vapor addition serves to inhibit the etching of the TiN base during the stripping process. The net result is a new manufacturing process which competes directly with conventional ashing and solvent processes in product performance; and which offers substantial cost savings through total elimination of solvent processing. Details of the parametric study of process conditions to achieve good TiN selectivity, excellent contact-resistance, and elimination of any TiN undercut will be discussed. A brief description of the manufacturing equipment involved will be included.