AVS 51st International Symposium
    Thin Films Monday Sessions
       Session TF-MoP

Paper TF-MoP16
Defect Study Post the Tungsten Etch Back Process Step

Monday, November 15, 2004, 5:00 pm, Room Exhibit Hall B

Session: Poster Session
Presenter: J. Zhang, STMicroelectronics, Inc.
Authors: A. Sidhwa, STMicroelectronics, Inc.
J. Zhang, STMicroelectronics, Inc.
V. Varadarjan, STMicroelectronics, Inc.
C. Li, STMicroelectronics, Inc.
B. Le, STMicroelectronics, Inc.
G. Magsamen, STMicroelectronics, Inc.
Correspondent: Click to Email
The tungsten etch back defects generated during the process with their relations to the wafer yield is studied in this paper. By understanding these defects the wafer yields can be improved and one can achieve maximum tool up time. For the tungsten etch-back (WEB) process, two kinds of processes are widely used in the manufacturing world: One is the pattern tungsten etch and the other is the blanket tungsten etch back. The tungsten etch back can either stop on titanium nitride (SOT) or stop on the oxide (SOX). This paper mainly focuses on the SOT process for the tungsten etch-back defects. During the Fluorine (F-) etch process; the F- ions from SF6 gas will etch the Tungsten (W) film at a faster rate as compared to the Titanium Nitride (TiN) film. Some of the TiN film will still be etched during the Tungsten Etch Back step. The by-products generated during the etch back step is in the form of titanium fluoride (TiFx). Sometimes the residual etch by-products are not completely pumped out of the chamber. The residual etch by-products may re-deposit on the chamber hardware which consists of the Aluminum and Aluminum Oxide parts. The residuals may react with chamber hardware generating TixAlx defects. In addition other defects are generated in the etch-back chamber. This paper describes a new kind of C, O, F, and Ti based particles observed after the tungsten etch back step at via levels. These defects were generated due to poor via cleaning process step which leaves the EKC residuals on the wafer. The residual defects on the wafers were hard to catch after via cleaning and after the Via Liner deposition process step. These residual defects would re-appear after the WEB process step. The mechanism of the formation of these defects is discussed in this paper along with method and implementation processes to reduce these defects.