AVS 51st International Symposium
    Plasma Science and Technology Tuesday Sessions
       Session PS2-TuM

Paper PS2-TuM5
Ru Etching Characteristics in Capacitively Coupled Ar/Cl@sub 2@/O@sub 2@ Plasma

Tuesday, November 16, 2004, 9:40 am, Room 213B

Session: New Gate Conductor Etching
Presenter: S. Rauf, Freescale Semiconductor
Authors: S. Rauf, Freescale Semiconductor
P.L.G. Ventzek, Freescale Semiconductor
V. Vartanian, Freescale Semiconductor
B. Goolsby, Freescale Semiconductor
S. Burnett, International Sematech
L. Chen, Tokyo Electron America Inc.
Correspondent: Click to Email
As the semiconductor industry attempts to replace the traditional gate dielectric, SiO@sub 2@, with higher-@kappa@ dielectrics (e.g., HfO@sub 2@), a thin metal layer need to be introduced in-between poly-silicon and gate dielectric to control conductor-dielectric interface properties. Ru is one metal that is being considered for this application. Along with electrical characteristics, the metal etching properties and compatibility of metal etch chemistry with other materials will determine how suitable a particular metal is for use in transistor gates. This paper describes a combined experimental and computational modeling investigation of Ru etching characteristics in a commercial dual frequency capacitively coupled Ar/Cl@sub 2@/O@sub 2@ plasma. Experiments explored the impact of gas mixture, RF power, gas pressure, and wafer temperature on Ru etch rate. Fourier transform infrared spectroscopy was also used to analyze effluents downstream from the plasma. Computational modeling was done using Io, a 2-dimensional plasma equipment simulation code. Plasma modeling results and blanket wafer etch rates were used to put together the Ru etch mechanism. Results indicate that reactive ion etching is the dominant Ru etch process, where O is first absorbed on Ru surface (generating RuO@sub x@) and the resulting compound is sputtered by energetic ions. The model captures experimental etch rate trends well at low gas pressures, but there is disparity between model and experiment at higher pressures. This difference is likely due to thermalization of sputtered Ru and RuO@sub x@ in the plasma, whose plasma chemistry is not well understood and, therefore, not accurately captured in our plasma chemical mechanism.