Radio Frequency Magnetron Sputtering Plasma Research Articles

Characteristics of a rotational windmill-shaped radio frequency magnetron sputtering plasma for effective target utilization

A rotational windmill-shaped radio frequency magnetron plasma source has been developed for improving the target utilization rate. Two kinds of magnet arrangements are designed by taking into account the E × B drift motion of electrons using simulated magnetic field profiles, where the electric field, E, is vertical to the target and the magnetic field, B, is parallel to the target, respectively. It is found that the Hall parameters of the electrons in the magnetron area have a higher value ranging from 12 to 110 for both magnet arrangements. This is high enough to magnetize electrons, while the electron Larmor radius is as low as 0.3–2.8 mm. The target utilization rate has attained approximately 65 % and 70 % for an initial and for an improved magnet arrangements, respectively. The improved magnet arrangement has a uniform profile of the target erosion compared with the initial magnet arrangement.

Numerical Investigation on Ion Inertia Force in Low-Temperature Plasma Using Fluid Model Considering Ion Momentum Equation

In this paper, we would like to numerically investigate the effect of ion inertia force in a typical argon gas discharge using fluid model considering the ion momentum equation, which becomes important under various operating conditions. The proposed self-consistent fluid model consists of the electron continuity equation with the drift-diffusion approximation, the ion continuity equation, the electron energy density equation, the ion momentum equation, and the Poisson equation for electric potential. We studied the plasma properties affected by the inertia force by comparing between the use of momentum equation and drift-diffusion approximation for ion momentum. The results show that the ion inertia force is significant under the low-pressure conditions (<100 mtorr) as expected, e.g., for plasma etching and radio frequency magnetron sputtering plasma. In addition, we also found when the pressure is higher than 100 mtorr, the inertia force becomes important (e.g., more than 15%) in the sheath region when the driving frequency is high enough (e.g., 60 MHz), e.g., for high-frequency plasma-enhanced chemical vapor deposition. Thus, inclusion of inertia force in the modeling of momentum equation becomes necessary under these operating conditions.

Experimental studies of first mirror exposure and surface recovery on EAST

Systematic studies of first mirrors (FMs) contamination, deposition mitigation and cleaning have been performed in EAST and laboratory. It turned out that the auxiliary systems such as gas puffing, wall conditioning and limiters could lead to a serious deposition on FMs and result in at least 60% degradation of the reflectivity. Besides, the exposure environment and depth–diameter ratios (DDRs) of the protective ducts will influence the degree of deposition mitigation and homogeneity of deposition. The reflectivity of the FM protected with duct at the wavelength of 240–400nm could sharply decrease at the beginning of the exposure, which differs from that in the wavelength range more than 400nm. In addition, the total and specular reflectivity of FM cleaned by radio frequency magnetron sputtering plasma (RFMSP) could be recovered by up to 90% and 80 % respectively in the wavelength range of 300–800nm.

Cleaning of HT-7 Tokamak Exposed First Mirrors by Radio Frequency Magnetron Sputtering Plasma

The stainless steel (SS) first mirror pre-exposed in the deposition-dominated environment of the HT-7 tokamak was cleaned in the newly built radio frequency (RF) magnetron sputtering plasma device. The deposition layer on the FM surface formed during the exposure was successfully removed by argon plasma with a RF power of about 80 W and a gas pressure of 0.087 Pa for 30 min. The total reflectivity of the mirrors was recovered up to 90% in the wavelength range of 300–800 nm, while the diffuse reflectivity showed a little increase, which was attributed to the increase of surface roughness in sputtering, and residual contaminants. The FMs made from single crystal materials could help to achieve a desired recovery of specular reflectivity in the future.

Effect of oxygen on the characteristics of radio frequency planar magnetron sputtering plasma used for aluminum oxide deposition

The characteristics of a radio frequency magnetron sputtering plasma are studied with the help of compensating Langmuir probe and optical emission spectroscopy in both reactive and nonreactive modes in argon and oxygen environment. Langmuir probe is used to measure the electron temperature, while the optical emission spectroscopy is used to get an idea about the relative concentration of metal and metal oxide formed under the different discharge conditions of argon and oxygen flow. The root mean square value of the discharge voltage and dc negative self-bias are found to be dependent on the oxygen flow rate as well as total gas pressure of the discharge. The study clearly shows the transition of the discharge from the metallic mode to the reactive mode with the increasing flow rate of oxygen, which strongly influences the sputtering. The optimum values of the control variables have been determined for the formation of aluminum oxide.