Real-Time In Situ Parallel Detection of Elements and Molecules with TOFMS during ALD for Chemical Quality Control of Thin Films

Abstract

The extraordinary properties of thin films result from their 2D structure, (i.e., one dimension is negligibly small when compared with the two others). Consequently, precise and well-established fabrication methods are required to provide appropriate functionality of these materials, such as hardness, resistance to mechanical stress, durability, or chemical/electrical stability. In this work, we present the potential of integrating a time-of-flight mass spectrometer (TOFMS) with atomic layer deposition (ALD) for real-time control of thin-film fabrication processes. This technique provides parallel detection of all ionized molecules and ionized fragments; therefore, the limitations of commonly used quadrupole mass spectrometers are overcome. Furthermore, since the chemical data acquisition is conducted in situ, the results of applied deposition parameters can be observed on-line allowing for immediate modifications, for example, in the case of process deviation from optimal or failure. The presented monitoring method is expected to be broadly applied in many deposition or etching processes, in which accurate chemical composition and strict end point control are demanded, such as manufacture of microdevices (for new energy solutions and microelectronics), protective surface coatings, actuators, sensors, and biomedical applications

Energy-Resolving Time-of-Flight Mass Spectrometry for Bulk Plasma Analysis

“…Examples of such areas include the development of high entropy alloy or compound films, where the energy of the impinging species influences the structure and microstructure of the grown film, ,,, or optimisation of thin film systems and interfaces in electronics, photovoltaics, and energy storage. The presented applications focus on PVD, specifically magnetron sputtering, however, it is likely that it will prove to be useful in the context of plasma enhanced chemical vapor deposition and atomic layer deposition (PE-CVD, PE-ALD) in general, where information on the IEDF and the nature of the ionic species involved in film growth are important for understanding the growth mechanism. Such measurements using conventional energy-resolving QMS systems would be greatly hindered, as it is not possible to measure more than a single m/Q ratio at a time, making it more difficult to follow ongoing plasma discharge processes and/or identify and characterise process instabilities, with the E-TOFMS additionally offering improved m/Q and E/Q resolution.…”

“…In comparison, TOFMS has the intrinsic ability to measure m/Q ratios quasi-simultaneously over a large mass range, with significantly higher mass resolution. 27 This work presents an energy-resolved TOFMS (E-TOFMS) that combines well-established TOFMS with an ESA, to allow for simultaneous identification of plasma ion species (m/Q range deliberately limited to 250 Th, however, can be increased up to 6000 Th) including their energy-tocharge (E/Q) ratio. Other ion energy filter design concepts, such as mirror-type and deflector plate analysers, have been extensively discussed in literature 28 and used in combination with QMS 29 and TOFMS 30 systems.…”

“…However, when multiple elements and isotopes need to be detected consecutively, the duty cycle is divided by the number of m/Q ratios of interest, which significantly reduces the duty cycle in the context of complex applications, such as (co-) sputtering of multiple and/or alloyed targets. In comparison, TOFMS has the intrinsic ability to measure m/Q ratios quasi-simultaneously over a large mass range, with significantly higher mass resolution …”