Ionized physical vapor deposition (IPVD): A review of technology and applications

Abstract

In plasma-based deposition processing, the importance of low-energy ion bombardment during thin film growth can hardly be exaggerated. Ion bombardment is an important physical tool available to materials scientists in the design of new materials and new structures. Glow discharges and in particular the magnetron sputtering discharge have the advantage that the ions of the discharge are abundantly available to the deposition process. However, the ion chemistry is usually dominated by the ions of the inert sputtering gas while ions of the sputtered material are rare. Over the past few years, various ionized sputtering techniques have appeared that can achieve a high degree of ionization of the sputtered atoms, often up to 50 % but in some cases as much as approximately 90%. This opens a complete new perspective in the engineering and design of new thin film materials. The development and application of magnetron sputtering systems for ionized physical vapor deposition (IPVD) is reviewed. The application of a secondary discharge, inductively coupled plasma

An introduction to thin film processing using high-power impulse magnetron sputtering

“…[19][20][21] When the deposition flux consists of more ions than neutrals, the process is referred to as ionized PVD or IPVD. 5 There are a few different IPVD techniques available today, such as postvaporization ionization using a secondary plasma generated by, for example, an RF coil placed in the deposition chamber to create ions that can be accelerated to the substrate surface when applying a negative bias. 22 Another technique is the previously mentioned cathodic arc evaporation (see references 23 and 24), which uses the fact that very localized, extremely high current discharges can create a dense plasma resulting in a high degree of ionization around a particular spot.…”

“…The length of the pulse is often kept in the range 10-500 ls 28,29 with a pulse frequency from tens of hertz to kilohertz. 5,30 The applied voltage during the pulse in most HiPIMS processes is usually around 500-1000 V, and the peak current density (peak discharge current/target area) reaches at most a few amperes per square centimeter (see Ref. 31).…”

“…12 This process is particularly efficient in HiPIMS discharges owing to the degree of ionization of the Ta vapor of up to 70%. 5 Ta forms both a low resistivity bodycentered cubic crystal structure (also known as the a phase) at elevated temperatures and a metastable high resistivity tetragonal phase (b-Ta) at room temperatures. 108,109 The abundance of Ta + ions in the deposition flux during the HiPIMS deposition of Ta films implies a more efficient momentum transfer to the growing surface.…”

“…5 To distinguish this technique from other pulsed magnetron processes, we use a similar definition as that of Anders 6 : HiPIMS is pulsed magnetron sputtering, where the peak power exceeds the time-averaged power by typically two orders of magnitude. In addition, the HiPIMS technology has recently been industrially upscaled by several big coating companies under various acronyms, which is a promising first step toward implementing it in common thin film processes.…”

“…The aim has been to provide a good introduction to this novel technique for PVD process engineers and researchers on thin films, who are familiar with the sputtering basics, without any claims on completely covering the whole field of HiPIMS. More details on the fundamentals and applications of HiPIMS can be found in the review articles by Helmersson et al, 5 Sarakinos et al, 18 and Anders. 6 Furthermore, it should also be brought to the readers' attention that parts of the current review concerning thin film processing are based on a recent review paper by Sarakinos et al 18 Moreover, in this work, much attention has been paid to different industrially relevant material systems owing to the fact that they are after all the ultimate goal of any thin film deposition process.…”