Quadrupole mass spectrometry of reactive plasmas

Abstract

Reactive plasmas are highly valued for their ability to produce large amounts of reactive radicals and of energetic ions bombarding surrounding surfaces. The non-equilibrium electron driven plasma chemistry is utilized in many applications such as anisotropic etching or deposition of thin films of high-quality materials with unique properties. However, the non-equilibrium character and the high power densities make plasmas very complex and hard to understand. Mass spectrometry (MS) is a very versatile diagnostic method, which has, therefore, a prominent role in the characterization of reactive plasmas. It can access almost all plasma generated species: stable gas-phase products, reactive radicals, positive and negative ions or even internally excited species such as metastables. It can provide absolute densities of neutral particles or energy distribution functions of energetic ions. In particular, plasmas with a rich chemistry, such as hydrocarbon plasmas, could not be understood without MS. This review focuses on quadrupole MS with an electron impact ionization ion source as the most common MS technique applied in plasma analysis. Necessary information for the understanding of this diagnostic and its application and for the proper design and calibration procedure of an MS diagnostic system for quantitative plasma analysis is provided. Important differences between measurements of neutral particles and energetic ions and between the analysis of low pressure and atmospheric pressure plasmas are described and discussed in detail. Moreover, MS-measured ion energy distribution functions in different discharges are discussed and the ability of MS to analyse these distribution functions with time resolution of several microseconds is presented.

Origin of the energetic ions at the substrate generated during high power pulsed magnetron sputtering of titanium

“…Since the spoke rotates with a frequency of 100 kHz around the racetrack, this period has to be compared with the transit time. This temporal broadening is identical to the broadening mechanism of IEDFs in RF sheaths [41], where a frequency of 100 kHz induces a significant broad IEDF. It would be interesting to generate data where the spoke rotation frequency can be freely adjusted and to correlate this to the width of the HE peak.…”

Insight into the Reaction Scheme of SiO2 Film Deposition at Atmospheric Pressure

“…They are connected through orifices aligned on one axis with a sampling orifice, forming a molecular beam of sampled particles in the low background density environment (pressure typically < 10 −3 Pa). An ioniser or ion extraction optics of a mass spectrometer is then used in the last stage with the lowest pressure to analyse the composition of the molecular beam, where both charged or neutral species can be measured . We use a modified system with a special chopper with rotating skimmer, which allows the measurement of high density molecular beam with very good background pressure (beam‐to background ratio more than 10).…”

“…We use a modified system with a special chopper with rotating skimmer, which allows the measurement of high density molecular beam with very good background pressure (beam‐to background ratio more than 10). More details can be found elsewhere …”

Precise in situ etch depth control of multilayered III−V semiconductor samples with reflectance anisotropy spectroscopy (RAS) equipment

“…There are various approaches to monitor and control the etch depth during dry-etching: With methods based on gas-phase analysis such as mass spectrometry of the residual gas [12] or optical gas-phase analysis such as optical emission spectroscopy [13–14] it is possible to achieve an end-point control [11,13,15]. In this case information on the actual etch depth can only be retrieved in connection with changes in material composition at the interfaces between any two layers.…”