AVS 46th International Symposium
    Electronic Materials and Processing Division Thursday Sessions
       Session EM1-ThA

Paper EM1-ThA5
Tungsten CMP Process Post Tungsten Etch Back Process to Improve the Reliability for Sub-Micron Device Technology

Thursday, October 28, 1999, 3:20 pm, Room 608

Session: Chemical Mechanical Planarization
Presenter: A. Sidhwa, STMicroelectronics, Inc.
Authors: A. Sidhwa, STMicroelectronics, Inc.
H. Minssieux, STMicroelectronics, Inc.
C. Spinner, STMicroelectronics, Inc.
Correspondent: Click to Email
In this paper we will discuss the importance of the CMP process used on wafers after the Tungsten Etch Back step. The purpose of the CMP step was to polish of the remaining Tungsten residue from the etch back process along with the Ti/TiN (barrier) layer and stop on the PMD layer. In the back end of the process, metal residues have been a killer defect that can cause significant decrease in the wafer yield. Residue remaining on the underlying surface may cause shorting of the conductive film and create defects that can affect planarity of the top film. Residues seen after tungsten etch back were due to incomplete tungsten etch back process in uneven areas. These residues can impact the metallization, patterning, and etch processes by causing broken metal lines or lines with defects. It is a known fact that during the tungsten etch back process; it is difficult to etch tungsten of the uneven surfaces due to under layer effects. Hence, high defects can be obtained after the WEB (tungsten etch back) step. If the CMP is performed to polish the remaining tungsten residue along with the barrier, most of the defects that were observed by the KLA after WEB step can be completely removed. The number of defects can be reduced drastically after CMP process. A considerable yield improvement due to CMP touch up process can be obtained. In this paper we show a short loop wafer yield map with high defects and compared to the KLA map performed after WEB process, the yield loss on the short loop wafer is directly correlated to the defects observed at the center of the wafer. This paper will show the defects before CMP and defects after CMP touch up step. Also it will discuss the impact on the electrical data and the SWEAT electromigration data due to Tungsten CMP touch up process.