AVS 50th International Symposium
    Plasma Science and Technology Tuesday Sessions
       Session PS-TuM

Paper PS-TuM11
Analysis of Downstream Etch Chemistry in Ion-Ion and Electron-Ion Cl2 Discharges

Tuesday, November 4, 2003, 11:40 am, Room 314

Session: Plasma Diagnostics: Processing
Presenter: A.K. Jindal, University of Texas at Dallas
Authors: A.K. Jindal, University of Texas at Dallas
A.J. Prengler, University of Texas at Dallas
L.J. Overzet, University of Texas at Dallas
M.J. Goeckner, University of Texas at Dallas
Correspondent: Click to Email
It has been shown that ion-ion plasmas can significantly reduce substrate charging damage. This study clearly shows that ion-ion plasmas also influence the etch chemistry. This knowledge may facilitate improvements in plasma processing or environmental control. Here, we use FTIR spectroscopy to examine the volatile etch products downstream of the turbo pump resulting from the etching of C-Si, SiO2, and photoresist in electron-ion and ion-ion Cl2 discharges. RF power is either pulsed to produce ion-ion plasmas or continuous to produce electron-ion plasmas. An independently controlled chuck is rf biased to produce an alternating flux of negative and positive ions or a combination of electrons, negative ions, and positive ions at the substrate. Changes in etch chemistry are studied and compared as functions of biasing schemes and substrate chuck voltages. Continuous wave (electron-ion), asynchronous, and synchronous, biasing regimes are all subjected to peak to peak chuck biases of 25, 50, 75, and 100 V via a 300 kHz waveform. Asynchronous and synchronous (ion-ion) modes apply to 1 kHz, 50 percent duty ratio pulsed regimes of the discharge in which the former implies continuous biasing throughout the entire pulse cycle and the latter to only the afterglow, where an ion-ion plasma exists. Clear distinctions in etch chemistry are evident solely based upon the biasing scheme. For example, CO2 is observed for all chuck biases in both pulsed regimes during photoresist etch, but no signal is apparent at lower biases in the continuous mode. Not only is there an undeniable difference in etch chemistry, but we can affect our emission by varying the biasing scheme. This work was funded in part by a grant from NSF/DOE, contract number CTS-0078669 and a grant from NSF, contract number CTS-0079783.