Jason A. Kenney

Three-dimensional model of magnetized capacitively coupled plasmas

A three-dimensional plasma model is used to understand the characteristics of magnetized capacitively coupled plasma discharges. The simulations consider plasmas generated using high frequency (13.5 MHz) and very high frequency (162 MHz) sources, electropositive (Ar) and electronegative (O2) gases, and spatially uniform and nonuniform magnetic fields. Application of a magnetic field parallel to the electrodes is found to enhance the plasma density due to improved electron confinement and shift the plasma due to the E×B drift. The plasma is electrically symmetric at 162 MHz so it drifts in opposite directions adjacent to the two electrodes due to the E×B drift. On the other hand, the 13.5 MHz plasma is electrically asymmetric and it predominantly moves in one direction under the influence of the E×B drift. The E×B drift focuses the plasma into a smaller volume in regions with convex magnetic field lines. Conversely, the E×B drift spreads out the plasma in regions with concave magnetic field lines. In a mag...

Influence of inhomogeneous magnetic field on the characteristics of very high frequency capacitively coupled plasmas

The effect of inhomogeneous magnetic field on the spatial structure of very high frequency (VHF) plasmas is investigated for different coil configurations, gas pressures, high frequency bias powers, and degrees of electronegativity. The simulation results show that the electron density peaks in the center of the chamber for VHF plasmas due to the standing electromagnetic wave effect. On application of a magnetic field, the density increases near the wafer edge and decreases at the chamber center. The radial magnetic field component is found to limit electron loss to the electrodes and locally enhance the electron density. The axial magnetic field component limits plasma diffusion in the radial direction helping preserve the effect of improved electron confinement by the radial magnetic field. The peak electron density decreases with increasing magnetic field as the plasma moves toward the electrode edge occupying a larger volume. The effect of magnetic field becomes weaker at higher pressure due to the in...

Effect of azimuthally asymmetric reactor components on a parallel plate capacitively coupled plasma

A three-dimensional fluid plasma model is used to investigate the impact of azimuthally asymmetric reactor components on spatial characteristics of parallel plate capacitively coupled plasmas. We consider three scenarios: high frequency (13.56 MHz) argon discharges with, separately, an off-axis circular plate surrounding the bottom electrode and an access port opening in the reactor sidewall, and a very high frequency (162 MHz) argon discharge with nonparallel electrodes. For the reactor with off-axis plate, both the Ar+ density and flux are strongly perturbed toward the direction of maximum grounded surface area, with azimuthal variation in ion flux up to 10%. Perturbations in Ar+ density due to the access port opening are localized to the region near the access port, and the impact on ion flux in the interelectrode region is minimal. Finally, the nonparallel electrodes result in a significant change in the location and shape of the Ar+ density profile, going from a center-peaked discharge with parallel ...

Atomic precision etch using a low-electron temperature plasma

Sub-nm precision is increasingly being required of many critical plasma etching processes in the semiconductor industry. Accurate control over ion energy and ion/radical composition is needed during plasma processing to meet these stringent requirements. Described in this work is a new plasma etch system which has been designed with the requirements of atomic precision plasma processing in mind. In this system, an electron sheet beam parallel to the substrate surface produces a plasma with an order of magnitude lower electron temperature Te (~ 0.3 eV) and ion energy Ei (< 3 eV without applied bias) compared to conventional radio-frequency (RF) plasma technologies. Electron beam plasmas are characterized by higher ion-to-radical fraction compared to RF plasmas, so a separate radical source is used to provide accurate control over relative ion and radical concentrations. Another important element in this plasma system is low frequency RF bias capability which allows control of ion energy in the 2-50 eV range. Presented in this work are the results of etching of a variety of materials and structures performed in this system. In addition to high selectivity and low controllable etch rate, an important requirement of atomic precision etch processes is no (or minimal) damage to the remaining material surface. It has traditionally not been possible to avoid damage in RF plasma processing systems, even during atomic layer etch. The experiments for Si etch in Cl2 based plasmas in the aforementioned etch system show that damage can be minimized if the ion energy is kept below 10 eV. Layer-by-layer etch of Si is also demonstrated in this etch system using electrical and gas pulsing.

Fully Self-Consistent 3-D Modeling of Inductively Coupled Plasmas

Inductively coupled plasma (ICP) reactors utilize multidimensional antenna segments among other azimuthally asymmetric components. Computed 3-D electric fields, power deposition, and electron density are presented for an ICP using a 3-D electromagnetic plasma model, which self-consistently treats the electromagnetic phenomena and the antenna-plasma coupling.

Modeling of Plasma Processing Equipment—Current Trends and Challenges

Plasma modeling is a critical technology for the design of industrial plasma processing systems. Plasma processes are increasingly being extended to the sub‐20 mTorr regime in the microelectronics industry, requiring accurate plasma models in the low pressure regime. Simultaneously, economic considerations are imposing stringent requirements on plasma uniformity over large substrates and plasma modeling is expected to address these uniformity challenges. These trends are necessitating good theoretical understanding in low temperature plasmas of (a) kinetic phenomena at low pressures and (b) the complex interplay between plasma, electromagnetic, chemical and fluid dynamics phenomena in three dimensions. Several fluid and particle‐in‐cell models are used in this paper to address issues of importance to the design and use of plasma etching and deposition systems.