IUVSTA 15th International Vacuum Congress (IVC-15), AVS 48th International Symposium (AVS-48), 11th International Conference on Solid Surfaces (ICSS-11)
    Manufacturing Science and Technology Tuesday Sessions
       Session MS-TuA

Paper MS-TuA3
Chamber Wall Monitoring and Control for Plasma Etching Reproducibility

Tuesday, October 30, 2001, 2:40 pm, Room 131

Session: In Line and In Situ Process Control
Presenter: E.S. Aydil, University of California, Santa Barbara
Authors: S.J. Ullal, University of California, Santa Barbara
T.-W. Kim, University of California, Santa Barbara
H. Singh, Lam Research Corporation
J. Daugherty, Lam Research Corporation
V. Vahedi, Lam Research Corporation
E.S. Aydil, University of California, Santa Barbara
Correspondent: Click to Email
Wafer-to-wafer process reproducibility is one of the major concerns in plasma etching of thin films. Production of a uniform plasma with the same ion density, electron temperature, and species concentrations wafer after wafer is a major challenge. The plasma chamber walls play a crucial role in determining these discharge properties and remain as one of the major sources of irreproducibility. The problem of process sensitivity to the wall conditions has been known for a long time but its management has remained an art. Thus, it is critical to monitor the wall conditions and the nature of the films and adsorbates that are deposited on the walls. Towards this end, we have developed a surface probe based on in situ multiple total internal reflection Fourier transform infrared (MTIR-FTIR) spectroscopy that can be used as a diagnostic to monitor the films and adsorbates on the walls of both plasma etching and deposition reactors. This surface probe was used to study the nature of the species present on the walls of the chamber and process repeatability during Cl@sub 2@/O@sub 2@ plasma etching of Si. This etching process is particularly challenging because SiCl@sub x@ etching products react with O atoms to deposit a SiO@sub x@ Cl@sub y@ film on the chamber walls, which must be cleaned with an SF@sub 6@ plasma to ensure reproducible wall conditions. Infrared spectra of the films depositing on the walls were collected in real time during Cl@sub 2@/O@sub 2@ plasma etching of Si and during the SF@sub 6@ cleaning steps to determine and monitor the effect of each process step and the reproducibility of cleaning. The surface probe was used to minimize the duration of the cleaning step to maximize throughput and to develop cleaning strategies to improve wafer-to-wafer repeatability. Subtle drifts in etch profile shapes could be detected through the use of the MTIR-FTIR probe even though these drifts are not detected through etch rate measurements and other monitoring methods.