Langmuir probe studies of a transformer-coupled plasma, aluminum etcher
- Bell Laboratories, Lucent Technologies, Murray Hill, New Jersey 07974 (United States)
Spatially resolved positive ion densities (n{sub i}{sup +}), electron densities (n{sub e}), electron temperatures (T{sub e}), plasma potentials (V{sub p}), and floating potentials (V{sub f}) were measured with a scanning Langmuir probe (PMT FastProbe) in Cl{sub 2} and BCl{sub 3}/Cl{sub 2}, inductively coupled plasmas (Lam Research Alliance, transformer-coupled plasma (TCP) metal etcher with a high-flow chamber). Time-resolved ion saturation current was measured during etching of Al/TiN metal stacks. Device damage during the metal stack etching was also studied. Positive ion densities increase nearly linearly with power for all of the gases. The maximum plasma density in the reactor is independent of pressure. The density profiles in the plane of the wafer are peaked above the center of the wafer at low pressure and off center at high pressure. Peaking off center is enhanced for smaller height-to-radius ratio chamber configurations, varied by changing the TCP window{endash}wafer chuck gap. The n{sub i}{sup +} uniformity across the wafer depends weakly on power, more strongly on feed gases and radio frequency bias, and most strongly on pressure and the TCP window{endash}wafer gap. Within experimental error, T{sub e} is uniform across the reactor at most pressures with a slight fall off beyond the wafer edge. At the lowest pressure, T{sub e} dips slightly in the center of the reactor. Addition of 28{percent} BCl{sub 3} to a Cl{sub 2} plasma causes a 20{percent} decrease in T{sub e} due to a decrease in the effective ionization potential of the gas. A small, grounded aluminum electrode was inserted into the plasma to eliminate perturbations from the Langmuir probe on the plasma, caused by charging and discharging of the insulating walls of the reactor. Such perturbations make apparent T{sub e}, V{sub f}, and V{sub p}, values too high, and at least partly explain why T{sub e}{close_quote}s measured with the Langmuir probe were higher than those obtained from optical emission spectroscopy. {copyright} {ital 1999 American Vacuum Society.}
- OSTI ID:
- 321486
- Journal Information:
- Journal of Vacuum Science and Technology, A, Vol. 17, Issue 2; Other Information: PBD: Mar 1999
- Country of Publication:
- United States
- Language:
- English
Similar Records
On the interest of carbon-coated plasma reactor for advanced gate stack etching processes
Metastable chlorine ion kinetics in inductively coupled plasmas