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The effect of a uniform magnetic field on particle transport in low-pressure radio frequency (RF) capacitively coupled plasma (CCP) has been studied using a particle-in-cell model. Three distinct regimes of plasma behavior can be identified as a function of the magnetic field. In the first regime at low magnetic fields, asymmetric plasma profiles are observed within the CCP chamber due to the effect of E → × B → drift. As the magnetic field increases, instabilities develop and form self-organized spoke-shaped structures that are distinctly seen within the bulk plasma closer to the sheath. In this second regime, the spoke-shaped coherent structures rotate inside the plasma chamber in the − E → × B → direction, where E → and B → are the DC electric and magnetic field vectors, respectively, and the DC electric field exists in the sheath and pre-sheath regions. The spoke rotation frequency is in the megahertz range. As the magnetic field strength increases further, the rotating coherent spokes continue to exist near the sheath. The coherent structures are, however, accompanied by new small-scale incoherent structures originating and moving within the bulk plasma region away from the sheath. This is the third regime of plasma behavior. The threshold values of the magnetic field between these regimes were found not to vary with changing plasma reactor geometry (e.g., area ratio between ground and powered electrodes) or the use of an external capacitor between the RF-powered electrode and the RF source. The threshold values of the magnetic field between these regimes shift toward higher values with increasing gas pressure. Analysis of the results indicates that the rotating structures are due to the lower hybrid instability driven by density gradients and electron-neutral collisions. This paper provides guidance on the upper limit of the magnetic field for instability-free operation in low-pressure CCP-based semiconductor deposition and etch systems that use the external magnetic field for plasma uniformity control. [ABSTRACT FROM AUTHOR]

Low-temperature plasmas (LTPs) are essential to manufacturing devices in the semiconductor industry, from creating extreme ultraviolet photons used in the most advanced lithography to thin film etching, deposition, and surface modifications. It is estimated that 40%–45% of all process steps needed to manufacture semiconductor devices use LTPs in one form or another. LTPs have been an enabling technology in the multidecade progression of the shrinking of device dimensions, often referred to as Moore's law. New challenges in circuit and device design, novel materials, and increasing demands to achieve environmentally benign processing technologies require advances in plasma technology beyond the current state-of-the-art. The Department of Energy Office of Science Fusion Energy Sciences held a workshop titled Plasma Science for Microelectronics Nanofabrication in August 2022 to discuss the plasma science challenges and technical barriers that need to be overcome to continue to develop the innovative plasma technologies required to support and advance the semiconductor industry. One of the key outcomes of the workshop was identifying a set of priority research opportunities (PROs) to focus attention on the most strategic plasma science challenges to address to benefit the semiconductor industry. For each PRO, scientific challenges and recommended strategies to address those challenges were identified. This article summarizes the PROs identified by the workshop participants. [ABSTRACT FROM AUTHOR]

Self-organized structures that are spread perpendicular to the radio frequency (RF) current direction have been observed in low temperature RF capacitively coupled plasmas. A fluid plasma model that includes thermoelectric electron energy transport is used to understand how these structures form. The electron thermoelectric transport coefficient is calculated using Bolsig+ for different chemistries and is found to be large for Ar plasma. Thermoelectric electron energy transport, which is driven by particle diffusion, opposes electron thermal conduction and can localize the plasma, leading to periodic structures. To examine these structures in radio frequency (RF) capacitive plasmas, two-dimensional Ar plasma at 13.5 MHz is first simulated without and then with thermoelectric electron energy transport. The charged species densities are perturbed in the simulations, and the growth or decay of different modes with time is observed. The periodicity of the structure is found to be determined by the relative strength of thermoelectric electron energy transport compared to energy conduction and losses. The effect of operating variables such as chemistry and pressure and design variables such as inter-electrode gap and steps in the electrode have been studied. For Ar plasma as pressure is decreased, the plasma peaks become stronger since thermoelectric electron energy transport is enhanced. Within limits, steps in the electrodes can be used to control the location of the periodic structures. For N2 plasma, the periodic structure does not appear as thermoelectric electron energy transport is weak. The spacing between plasma peaks is found to be dependent on pressure, chemistry, and inter-electrode gap. [ABSTRACT FROM AUTHOR]

A coupled plasma equipment-surface physics model is used in conjunction with an experimental diagnostics of nitrided SiO2 thin films to understand the mechanism of SiO2 plasma nitridation and this investigation is conducted in pulsed inductively coupled plasma (ICP) of N2. The results show that the nitrogen transport and reaction properties in the film are film thickness dependent, probably due to the nonuniform density of the initial SiO2 thin film or to interfacial stresses.

Nonlinear interaction of two radio frequency (RF) sources in a magnetized Ar/[C.sub.2][F.sub.6] Fo capacitively coupled plasma discharge is investigated using a computational model. Results show that application of a radial magnetic field enhances charged and neutral species densities in the plasma reactor due to reduction in electron loss to surfaces and trapping of secondary electron emission generated electrons. Amplitude of RF currents at electrodes also increases with magnetic field strength and source frequency for a given RF voltage. Due to nonlinear nature of plasma sheath, higher harmonics of applied frequencies and source interaction generated harmonics can be observed in electrode currents. Application of magnetic field decreases electron mobility and makes the system less nonlinear, which reduces higher harmonics relative to primary components. Magnetic field also tends to make the RF sources more isolated. Increase in source frequency moves the plasma from electrode edge to the center of the chamber, which redistributes current through the electrodes. If frequencies of the two RF sources are commensurate, nonlinear interaction of RF sources generates subharmonics of primary frequencies. Index Terms--Capacitively coupled, dual frequency, magnetized plasma, magnetically enhanced reactive ion etching (MERIE), nonlinear interaction, plasma modeling, subharmonic generation.

Three rare gases He-Ar-Xe were used as the base of ionized physical vapor deposition of Cu.

The influence of the rf bias voltage waveform and frequency on ion energy distributions is studied. It is found that the sinusoidal waveform leads to a distribution that peaks at high energies and decreases gradually with decreasing energy.

Plasma display panels (PDPs) are one of the leading technologies for large-area high-brightness flat panel displays. Results from a two-dimensional model were employed to study the effects of operating conditions, gas mixture, cell dimensions and material characteristics on the visible light generation capacity of a coplanar-electrode PDP cell sustained in He/Ne/Xe gas mixtures. Gas mixtures with more Ne or less He were observed to provide more visible light at higher efficiency.

As microelectronics device feature sizes continue to shrink and wafers continue to increase in size, it is necessary to have tighter tolerances during the fabrication process to maintain high yields. Feedback control has, therefore, become an important issue in plasma processing equipment design. Comprehensive plasma equipment models linked to control algorithms would greatly aid in the investigation and optimal selection of control strategies. This paper reports on a numerical plasma simulation tool, the Virtual Plasma Equipment Model (VPEM), which addresses this need to test feedback control strategies and algorithms on plasma processing equipment. The VPEM is an extension of the Hybrid Plasma Equipment Model which has been augmented by sensors and actuators, linked together through a programmable controller. The sensors emulate experimental measurements of species densities, fluxes, and energies, while the actuators change process parameters such as pressure, inductive power, capacitive power, electrode voltages, and mole fraction of gases. Controllers were designed using a response surface based methodology. Results are presented from studies in which these controllers were used to compensate for a leak of [N.sub.2] into an Ar discharge, to stably control drifts in process parameters such as pressure and power in Ar and Ar/[Cl.sub.2], and to nullify the effects of long term changes in wall conditions in [Cl.sub.2] containing plasmas. A new strategy for improving the ion energy flux uniformity in capacitively coupled discharges using feedback control techniques is also explored.

Research was conducted to study the influence of radio frequency plasma processor reactor circuitry on plasma features. A plasma equipment model was utilized to investigate couplings and the effects of operating conditions, reactor geometry and stray coupling. Results showed that the plasma reactor was approximated by a set of interconnected sheaths and resistors. They also indicated that resulting currents and voltages had significant magnitudes at higher harmonics resulting from the nonlinear nature of the sheaths.

A two-dimensional computer simulation of Ar, Ar/O2 and Ar/CF4 discharges sustained in the Gaseous Electronics Conference reference cell were performed with the Hybrid Plasma Equipment Model. Results of the experiments indicate that the shift in Ar(4s) densities is largely explained by the reduction in the electron mean free path and local perturbations in the ambipolar electric field resulting from electrode structures. As small amounts of O2 and CF4 were added, the Ar density decreased due to quenching while its profile changed due to an electronegative plasma transition.

A two-dimensional fluid plasma model for a transformer-coupled toroidal plasma source is described. Ferrites are used in this device to improve the electromagnetic coupling between the primary coils carrying radio frequency (rf) current and a secondary plasma loop. Appropriate components of the Maxwell equations are solved to determine the electromagnetic fields and electron power deposition in the model. The effect of gas flow on species transport is also considered. The model is applied to 1 Torr Ar/NH3 plasma in this article. Rf electric field lines form a loop in the vacuum chamber and generate a plasma ring. Due to rapid dissociation of NH3, NHx+ ions are more prevalent near the gas inlet and Ar+ ions are the dominant ions farther downstream. NH3 and its by-products rapidly dissociate into small fragments as the gas flows through the plasma. With increasing source power, NH3 dissociates more readily and NHx+ ions are more tightly confined near the gas inlet. Gas flow rate significantly influences the plasma characteristics. With increasing gas flow rate, NH3 dissociation occurs farther from the gas inlet in regions with higher electron density. Consequently, more NH4+ ions are produced and dissociation by-products have higher concentrations near the outlet. [ABSTRACT FROM AUTHOR]

Capacitively coupled plasmas (CCPs) generated using high frequency (3-30 MHz) and very high frequency (30-300 MHz) radio-frequency (rf) sources are used for many plasma processing applications including thin film etching and deposition. When chamber dimensions become commensurate with the effective rf wavelength in the plasma, electromagnetic wave effects impose a significant influence on plasma behavior. Because the effective rf wavelength in plasma depends upon both rf and plasma process conditions (e.g., rf power and gas pressure), a self-consistent model including both the rf power delivery system and the plasma discharge is highly desirable to capture a more complete physical picture of the plasma behavior. A three-dimensional model for self-consistently studying both electrodynamic and plasma dynamic behavior of large-area (Gen 10, >8 m2) CCP is described in this paper. This model includes Maxwell's equations and transport equations for charged and neutral species, which are coupled and solved in the time domain. The complete rf plasma discharge chamber including the rf power delivery subsystem, rf feed, electrodes, and the plasma domain is modeled as an integrated system. Based on this full-wave solution model, important limitations for processing uniformity imposed by electromagnetic wave propagation effects in a large-area CCP (3.05×2.85 m2 electrode size) are studied. The behavior of H2 plasmas in such a reactor is examined from 13.56 to 200 MHz. It is shown that various rectangular harmonics of electromagnetic fields can be excited in a large-area rectangular reactor as the rf or power is increased. The rectangular harmonics can create not only center-high plasma distribution but also high plasma density at the corners and along the edges of the reactor. [ABSTRACT FROM AUTHOR]