| AVS 58th Annual International Symposium and Exhibition | |
| Plasma Science and Technology Division | Tuesday Sessions |
| Session PS1-TuA |
| Session: | Advanced BEOL / Interconnect Etching II |
| Presenter: | Sang-Heon Song, University of Michigan |
| Authors: | S.-H. Song, University of Michigan M.J. Kushner, University of Michigan |
| Correspondent: | Click to Email |
Feature scale etch or deposition properties in plasma processing of microelectronic devices are determined by the energies and fluxes of radicals and ions to the wafer. These fluxes are ultimately controlled by controlling and customizing the electron energy distribution function f(ε) which determines the dissociation patterns of feedstock gases and the relationship between applied power and sheath potential. One way to customize f(ε) in dual frequency capacitively coupled plasmas (CCPs) is using pulse power for either or both of the high frequency or low frequency. Pulsed power in CCPs is attractive for controlling f(ε) and plasma properties as it provides a means for producing combinations of fluxes (e.g., magnitude, identity and energy) not otherwise attainable using continuous wave excitation. In these systems, the choices of duty cycle and pulse repetition frequency (PRF) are important in determining the cycled average value of f(ε) and fI(ε) due to the role of thermalization of electrons during the afterglow. The ability to control f(ε) and fI(ε) may have both clear and subtle effects on the critical dimensions (CD) of etch features. For example, charge accumulation in the feature and the angular spread of ions may be controlled by the choice of duty cycle and PRF, both of which affect the etch profile. This enables some ability to control, for example, the sidewall slope of high-aspect-ratio (HAR) features by pulse-power formats. To demonstrate the ability to control feature profiles through control of f(ε) and fI(ε) using pulsed plasmas, simulations were performed separately in two regions – on the equipment scale using the Hybrid Plasma Equipment Model (HPEM) and on the feature scale using the Monte Carlo Feature Profile Model (MCFPM). The fluxes of radicals and ions to the wafer from the HPEM are transferred to the MCFPM to calculate the etch properties. Plasma properties, f(ε) and fI(ε,θ), and ratios of fluxes to the wafer for an Ar/CF4/O2 gas mixture in a 2-frequency CCP will be discussed. The tuning of etch rates and profiles of HAR features in SiO2 resulting from these fluxes will then be summarized.
* Work supported by the Department of Energy Office of Fusion Energy Sciences and the Semiconductor Research Corp.