Many-particle charged-particle plasma simulations using spatial meshes for the electromagnetic field solutions, particle-in-cell (PIC) merged with Monte Carlo collision (MCC) calculations, are coming into wide use for application to partially ionized gases. The author emphasizes the development of PIC computer experiments since the 1950s starting with one-dimensional (1-D) charged-sheet models, the addition of the mesh, and fast direct Poisson equation solvers for 2-D and 3-D. Details are provided for adding the collisions between the charged particles and neutral atoms. The result is many-particle simulations with many of the features met in low-temperature collision plasmas; for example, with applications to plasma-assisted materials processing, but also related to warmer plasmas at the edges of magnetized fusion plasmas. >

Particle-in-Cell Charged Particle Simulations, plus Monte Carlo Collisions with Neutral Atoms, PIC-MCC

Process gas discharged from a bypass pipe to a gas exhaust system can be prevented from diffusing back to the inside of a process chamber without having to install a dedicated vacuum pump at the downstream side of the bypass pipe. The substrate processing apparatus includes a process chamber accommodating a substrate, a gas supply system supplying process gas from a process gas source to the process chamber for processing the substrate, a gas exhaust system configured to exhaust the process chamber, two or more vacuum pumps installed in series at the gas exhaust system, and a bypass pipe connected between the gas supply system and the gas exhaust system. The most upstream one of the vacuum pumps is a mechanical booster pump, and the bypass pipe is connected between the mechanical booster pump and the rest vacuum pumps located at a downstream side of the mechanical booster pump.

Substrate Processing Apparatus

The field of plasma etching is reviewed. Plasma etching, a revolutionary extension of the technique of physical sputtering, was introduced to integrated circuit manufacturing as early as the mid 1960s and more widely in the early 1970s, in an effort to reduce liquid waste disposal in manufacturing and achieve selectivities that were difficult to obtain with wet chemistry. Quickly, the ability to anisotropically etch silicon, aluminum, and silicon dioxide in plasmas became the breakthrough that allowed the features in integrated circuits to continue to shrink over the next 40 years. Some of this early history is reviewed, and a discussion of the evolution in plasma reactor design is included. Some basic principles related to plasma etching such as evaporation rates and Langmuir–Hinshelwood adsorption are introduced. Etching mechanisms of selected materials, silicon, silicon dioxide, and low dielectric-constant materials are discussed in detail. A detailed treatment is presented of applications in current silicon integrated circuit fabrication. Finally, some predictions are offered for future needs and advances in plasma etching for silicon and nonsilicon-based devices.

/pdf/plasma-etching-yesterday-today-and-tomorrow-4a8eftp390.pdf

Plasma etching: Yesterday, today, and tomorrow

Cold plasma technology is an emerging, green process offering many potential applications for food packaging. While it was originally developed to increase the surface energy of polymers, enhancing adhesion and printability, it has recently emerged as a powerful tool for surface decontamination of both foodstuffs and food packaging materials. New trends aim to develop in-package decontamination, offering non-thermal treatment of foods post-packaging. This paper provides an overview of cold plasma theory, equipment and summarises recent advances in the modification of polymeric food packaging materials along with potential applications in the food industry.

Applications of cold plasma technology in food packaging

Bonded repair of composite aircraft structures: A review of scientific challenges and opportunities

Dual frequency capacitive discharges are designed to offer independent control of the flux and energy of ions impacting on an object immersed in a plasma. This is desirable in applications such as the processing of silicon wafers for microelectronics manufacturing. In such discharges, a low frequency component couples predominantly to the ions, while a high frequency component couples predominantly to electrons. Thus, the low frequency component controls the ion energy, while the high frequency component controls the plasma density. Clearly, this desired behaviour is not achieved for arbitrary configurations of the discharge, and in general one expects some unwanted coupling of ion flux and energy. In this paper we use computer simulations with the particle-in-cell method to show that the most important governing parameter is the ratio of the driving frequencies. If the ratio of the high and low frequencies is great enough, essentially independent control of the ion energy and flux is possible by manipulation of the high and low frequency power sources. Other operating parameters, such as pressure, discharge geometry, and absolute power, are of much less significance.

https://iopscience.iop.org/article/10.1088/0022-3727/37/5/008/pdf

Independent control of ion current and ion impact energy onto electrodes in dual frequency plasma devices

An industrial, confined, dual frequency, capacitively coupled, radio-frequency plasma etch reactor (Exelan®, Lam Research) has been modified for spatially resolved optical measurements. Space and phase resolved optical emission spectroscopy yields insight into the dynamics of the discharge. A strong coupling of the two frequencies is observed in the emission profiles. Consequently, the ionization dynamics, probed through excitation, is determined by both frequencies. The control of plasma density by the high frequency is, therefore, also influenced by the low frequency. Hence, separate control of plasma density and ion energy is rather complex.

http://www.fjschulze.de/Julian_Schulze_Homepage/Publications_files/Appl%20Phys%20Lett%202006%20Gans.pdf

Frequency coupling in dual frequency capacitively coupled radio-frequency plasmas

Particle-in-cell simulations have been used to study the nature of dual frequency plasma discharges. It is observed that both the ion flux on to the electrodes and the ion bombardment energy on to the electrodes can be controlled independently. There are two separate regimes in which this occurs. At large electrode separation, the ion current is controlled by varying the total discharge current, Jlf + Jhf. At small electrode separations, the ion flux can be controlled by varying the high frequency power source. In both regimes, the energy of the ions bombarding the electrodes is then determined by the low frequency voltage. A consequence of using dual frequencies to power the device is that the sheath width increases linearly as the low frequency power source is increased. This results in the dimensions of the bulk plasma decreasing, causing the electron temperature to increase for devices with electrode separations that are of comparable size to the electrode separation. In order to better understand the underlying physics involved within these devices an analytical global model has been developed which can explain many of the characteristics observed in the simulations.

http://iopscience.iop.org/article/10.1088/0963-0252/13/3/016/pdf

Electrostatic modelling of dual frequency rf plasma discharges

A semiconductor processing system includes a processing chamber system and an activated gas source coupled to the chamber system. The gas source includes a primary winding coupled to an RF generator and a secondary winding effectively formed by the conductance of a plasma filled passageway in a toroidal chamber. The primary winding and the secondary winding are coaxially aligned to provide a suitable inductive coupling between the windings.

Semiconductor processing using an efficiently coupled gas source

Vector‐rf‐B‐field measurements in the near‐field of a helicon plasma source taken throughout the volume of the source are reported. Three distinct modes of operation of the helicon plasma source, capacitive, inductive, and helicon‐wave, are identified by the structure of the plasma‐wave‐fields. Results are reported for a double‐half‐turn antenna, which is believed to be the first reporting for such an antenna structure in application to helicon‐wave plasma sources. Comparison is made to a double‐saddle‐coil antenna which also demonstrates the distinct inductive and helicon‐wave modes.

/pdf/capacitive-inductive-and-helicon-wave-modes-of-operation-of-4m5ymwimbt.pdf

Albert R. Ellingboe

Papers

Independent control of ion current and ion impact energy onto electrodes in dual frequency plasma devices

Frequency coupling in dual frequency capacitively coupled radio-frequency plasmas

Electrostatic modelling of dual frequency rf plasma discharges

Semiconductor processing using an efficiently coupled gas source

Capacitive, inductive and helicon‐wave modes of operation of a helicon plasma source