AVS 52nd International Symposium
    Plasma Science and Technology Tuesday Sessions
       Session PS-TuA

Paper PS-TuA4
Control of Surface Reactions during Organic Low-k Dry Etching

Tuesday, November 1, 2005, 3:00 pm, Room 302

Session: Dielectric Etch II
Presenter: S. Uchida, Nagoya University, Japan
Authors: S. Uchida, Nagoya University, Japan
M. Hori, Nagoya University, Japan
K. Oshima, Sony Corporation, Japan
A. Ando, Sony Corporation, Japan
K. Nagahata, Sony Corporation, Japan
T. Tatsumi, Sony Corporation, Japan
Correspondent: Click to Email
In the fabrication of Cu/low-k interconnect for 45-nm devices and beyond, precise control of plasma processes becomes indispensable. Hybrid dual damascene structures use organic low-k and SiOCH films for trench and via levels. The N-H-based plasma has been employed to fabricate SiLK@super TM@ trench patterns with high selectivity both to SiO@sub 2@ hard mask and to underlying SiOCH. First, to separate the effects of ion energy and radical compositions, the etching yield of SiLK@super TM@ was investigated by using a beam experiment apparatus with a radical injection system. An Ar@super +@ ion beam (100â?"500eV) was used to irradiate sample surfaces (SiLK@super TM@, SiOCH, and SiO@sub 2@) with supplying N and H radical fluxes. We quantitatively varied both the incident ion energy and the composition of the H/N radical fluxes. H and N radical densities were measured by in-situ vacuum ultraviolet absorption spectroscopy. The threshold ion energy for the SiLK@super TM@ etching was about 100 eV under the condition of H / (H + N) = 11%. The etch yield of SiLK@super TM@ strongly depended on the composition of the radical fluxes. We found that H radicals promoted reactions of N atoms with organic polymers. Consequently, the etch yield of SiLK@super TM@ dramatically increased when a small amount of H radicals (< 20%) were added to the N radicals. This result suggests that the stably controlling of the H radical density in N/H plasma and the incident ion energy in real etching systems is important. The high energy peak of the ion energy distribution function was controlled by adjusting the power and frequency in a CCP system. By decreasing the high energy peak (to decrease the etch yield of the hard mask) while keeping the ion current and etch yield high (to keep a high etch rate for SiLK@super TM@ to decrease the total etch time), we have successfully minimized the erosion of the hard mask and the variation of the critical dimension during SiLK@super TM@ trench fabrications.