AVS 58th Annual International Symposium and Exhibition
    Plasma Science and Technology Division Friday Sessions
       Session PS-FrM

Paper PS-FrM6
Magnetic Field - Plasma Interaction in Low Pressure VHF Capacitively Coupled Plasmas using PIC-MCC/Fluid Hybrid Model

Friday, November 4, 2011, 10:00 am, Room 201

Session: Plasma Modeling
Presenter: Kallol Bera, Applied Materials, Inc.
Authors: K. Bera, Applied Materials, Inc.
A. Agarwal, Applied Materials, Inc.
S. Rauf, Applied Materials, Inc.
K. Collins, Applied Materials, Inc.
Correspondent: Click to Email
Low pressure magnetized capacitively coupled plasmas are extensively used for advanced microelectronics device fabrication. Due to the long mean free path of electrons in this regime, kinetic effects characterize the plasma dynamics in low pressure discharges. To take into account the kinetic effects, a hybrid 2-dimensional (2D) plasma modeling software has been developed that couples a particle-in-cell (PIC) model for charged species with a fluid method for neutral species. The electron motion due to electric and magnetic fields is incorporated in 3-dimensional velocity space using the Lorentz force law. The PIC model uses the Monte Carlo Collision (MCC) method to account for collision processes. The fluid model for neutral species takes into account species transport in the plasma, chemical reactions, and surface processes. Capacitively coupled rf plasmas in Ar have been computationally investigated for a 2D parallel plate plasma reactor in Cartesian co-ordinates. The inter-electrode gap is 5 cm (in y-direction). The bottom electrode is powered using a 60 MHz very high frequency (VHF) source, and the top electrode is grounded. The two electrodes are separated by quartz inserts. Ar plasma is simulated for a range of magnetic fields (25 - 100 Gauss), pressures (10 - 50 mTorr) and rf voltages (100 - 300 Volts). In this range of magnetic fields, the electrons are magnetized due to a small Larmor radius while the ions remain non-magnetized. For a symmetric reactor configuration without magnetic field, the plasma is symmetric, and the peak in plasma density occurs at the center plane between the top and bottom electrodes. The electron density increases with increase in pressure and rf voltage. With magnetic field in the x-direction (parallel to the electrodes), the plasma becomes more confined. When the magnetic field is applied in the z-direction, orthogonal to the electric field, the E x B drift is observed, and the plasma becomes asymmetric. When the magnetic field direction is reversed, E x B drift reverses, therefore, the direction of plasma asymmetry reverses. The effect of magnetic field on plasma symmetry will be examined. In addition, results from the kinetic simulation will be compared to corresponding results from a fluid plasma model.