High Power Impulse Magnetron Sputtering
Encyclopedia
High Power Impulse Magnetron Sputtering (HIPIMS, also known as High Power Pulsed Magnetron Sputtering, HPPMS) is a method for physical vapor deposition
of thin films which is based on magnetron sputter deposition
. HIPIMS utilises extremely high power densities of the order of kWcm−2 in short pulses (impulses) of tens of microseconds at low duty cycle
(on/off time ratio) of < 10%. A distinguishing feature of HIPIMS is its high degree of ionisation of the sputtered metal and high rate of molecular gas dissociation.
HIPIMS is used for:
The first US patent on HIPIMS was filed by Vladimir Kouznetsov (priority date 9 Dec 1997), Kouznetsov US 6296742 B1.
HIPIMS generates a high density plasma
of the order of 1013 ions cm−3 containing high fractions of target metal ions. The main ionisation mechanism is electron impact, which is balanced by charge exchange and diffusion. The ionisation rates depend on the plasma density.
The ionisation degree of the metal vapour is a strong function of the peak current density of the discharge. At high current densities, sputtered ions with charge 2+ and higher - up to 5+ for V - can be generated. The appearance of target ions with charge states higher than 1+ is responsible for a potential secondary electron emission process that has a higher emission coefficient than the kinetic secondary emission
found in conventional glow discharges. The establishment of a potential secondary electron emission may enhance the current of the discharge.
HIPIMS is typically operated in short pulse (impulse) mode with a low duty cycle
in order to avoid overheating of the target and other system components. In every pulse the discharge goes through several stages:
The discharge that maintains HIPIMS is a high-current glow discharge, which is transient or quasistationary. Each pulse remains a glow up to a critical duration after which it transits to an arc discharge
. If pulse length is kept below the critical, the discharge operates in a stable fashion infinitely.
or atomic registry is typical between the crystal of a nitride film and the crystal of a metal substrate when HIPIMS is used for pretreatment. HIPIMS has been used for the pretreatment of steel substrates for the first time in February 2001 by A.P. Ehiasarian.
Substrate biasing during pretreatment utilises high voltages, which require purpose-designed arc detection and suppression technology. Dedicated DC substrate biasing units provide the most versatile option as they maximize substrate etch rates, minimise substrate damage, and can operate in systems with multiple cathodes. An alternative way is the use of two HIPIMS power supplies synchronised in a master–slave configuration: one to establish the discharge and one to produce a pulsed substrate bias
s deposited by HIPIMS at discharge current density > 0.5 Acm−2 have a dense columnar structure with no voids.
The deposition of copper films by HIPIMS was reported for the first time by V. Kouznetsov for the application of filling 1 µm vias
with aspect ratio of 1:1.2
Transition metal
nitride
(CrN) thin films were deposited by HIPIMS for the first time in February 2001 by A.P. Ehiasarian. The first thorough investigation of films deposited by HIPIMS by TEM
demonstrated a dense microstructure, free of large scale defects. The films had a high hardness, good corrosion
resistance and low sliding wear
coefficient. This research paved the way to the first industrial upscaling of the technology in January 2004 at Sheffield Hallam University
, UK in collaboration with Advanced Converters, Warsaw, Poland (present day Hüttinger Electronics, Poland). The commercialisation of HIPIMS hardware that followed from this made the technology accessible to the wider scientific community and triggered developments in a wide range of areas.
The following materials have, amongst others, been deposited successfully by HIPIMS:
Physical vapor deposition
Physical vapor deposition is a variety of vacuum deposition and is a general term used to describe any of a variety of methods to deposit thin films by the condensation of a vaporized form of the desired film material onto various workpiece surfaces...
of thin films which is based on magnetron sputter deposition
Sputter deposition
Sputter deposition is a physical vapor deposition method of depositing thin films by sputtering, that is ejecting, material from a "target," that is source, which then deposits onto a "substrate," such as a silicon wafer...
. HIPIMS utilises extremely high power densities of the order of kWcm−2 in short pulses (impulses) of tens of microseconds at low duty cycle
Duty cycle
In engineering, the duty cycle of a machine or system is the time that it spends in an active state as a fraction of the total time under consideration....
(on/off time ratio) of < 10%. A distinguishing feature of HIPIMS is its high degree of ionisation of the sputtered metal and high rate of molecular gas dissociation.
HIPIMS is used for:
- adhesion enhancing pretreatment of the substrate prior to coating deposition (substrate etching)
- deposition of thin films with high microstructure density
The first US patent on HIPIMS was filed by Vladimir Kouznetsov (priority date 9 Dec 1997), Kouznetsov US 6296742 B1.
HIPIMS Plasma Discharge
HIPIMS plasma is generated by a glow discharge where the discharge current density can reach up to 6 Acm−2, whilst the discharge voltage is maintained at several hundred volts. The discharge is homogeneously distributed across the surface of the cathode of the chamber.HIPIMS generates a high density plasma
Plasma (physics)
In physics and chemistry, plasma is a state of matter similar to gas in which a certain portion of the particles are ionized. Heating a gas may ionize its molecules or atoms , thus turning it into a plasma, which contains charged particles: positive ions and negative electrons or ions...
of the order of 1013 ions cm−3 containing high fractions of target metal ions. The main ionisation mechanism is electron impact, which is balanced by charge exchange and diffusion. The ionisation rates depend on the plasma density.
The ionisation degree of the metal vapour is a strong function of the peak current density of the discharge. At high current densities, sputtered ions with charge 2+ and higher - up to 5+ for V - can be generated. The appearance of target ions with charge states higher than 1+ is responsible for a potential secondary electron emission process that has a higher emission coefficient than the kinetic secondary emission
Secondary emission
Secondary emission in physics is a phenomenon where primary incident particles of sufficient energy, when hitting a surface or passing through some material, induce the emission of secondary particles. The primary particles are often charged particles like electrons or ions. If the secondary...
found in conventional glow discharges. The establishment of a potential secondary electron emission may enhance the current of the discharge.
HIPIMS is typically operated in short pulse (impulse) mode with a low duty cycle
Duty cycle
In engineering, the duty cycle of a machine or system is the time that it spends in an active state as a fraction of the total time under consideration....
in order to avoid overheating of the target and other system components. In every pulse the discharge goes through several stages:
- electrical breakdownElectrical breakdownThe term electrical breakdown or electric breakdown has several similar but distinctly different meanings. For example, the term can apply to the failure of an electric circuit....
- gas plasma
- metal plasma
- steady state, which may be reached if the metal plasma is dense enough to effectively dominate over the gas plasma
The discharge that maintains HIPIMS is a high-current glow discharge, which is transient or quasistationary. Each pulse remains a glow up to a critical duration after which it transits to an arc discharge
Cathodic Arc Deposition
Cathodic arc deposition or Arc-PVD is a physical vapor deposition technique in which an electric arc is used to vaporize material from a cathode target. The vaporized material then condenses on a substrate, forming a thin film...
. If pulse length is kept below the critical, the discharge operates in a stable fashion infinitely.
Substrate pretreatement by HIPIMS
Substrate pretreatment in a plasma environment is required prior to deposition of thin films on mechanical components such as automotive parts, metal cutting tools and decorative fittings. The substrates are immersed in a plasma and biased to a high voltage of a few hundred volts. This causes high energy ion bombardment that sputters away any contamination. In cases when the plasma contains metal ions, they can be implanted into the substrate to a depth of a few nm. HIPIMS is used to generate a plasma with a high density and high proportion of metal ions. When looking at the film-substrate interface in cross-section, one can see a clean interface. EpitaxyEpitaxy
Epitaxy refers to the deposition of a crystalline overlayer on a crystalline substrate, where the overlayer is in registry with the substrate. In other words, there must be one or more preferred orientations of the overlayer with respect to the substrate for this to be termed epitaxial growth. The...
or atomic registry is typical between the crystal of a nitride film and the crystal of a metal substrate when HIPIMS is used for pretreatment. HIPIMS has been used for the pretreatment of steel substrates for the first time in February 2001 by A.P. Ehiasarian.
Substrate biasing during pretreatment utilises high voltages, which require purpose-designed arc detection and suppression technology. Dedicated DC substrate biasing units provide the most versatile option as they maximize substrate etch rates, minimise substrate damage, and can operate in systems with multiple cathodes. An alternative way is the use of two HIPIMS power supplies synchronised in a master–slave configuration: one to establish the discharge and one to produce a pulsed substrate bias
Thin Film Deposition by HIPIMS
Thin filmThin film
A thin film is a layer of material ranging from fractions of a nanometer to several micrometers in thickness. Electronic semiconductor devices and optical coatings are the main applications benefiting from thin film construction....
s deposited by HIPIMS at discharge current density > 0.5 Acm−2 have a dense columnar structure with no voids.
The deposition of copper films by HIPIMS was reported for the first time by V. Kouznetsov for the application of filling 1 µm vias
Via (electronics)
A via is a vertical electrical connection between different layers of conductors in a physical electronic circuit.- In IC :In integrated circuit design, a via is a small opening in an insulating oxide layer that allows a conductive connection between different layers. A via on an integrated circuit...
with aspect ratio of 1:1.2
Transition metal
Transition metal
The term transition metal has two possible meanings:*The IUPAC definition states that a transition metal is "an element whose atom has an incomplete d sub-shell, or which can give rise to cations with an incomplete d sub-shell." Group 12 elements are not transition metals in this definition.*Some...
nitride
Nitride
In chemistry, a nitride is a compound of nitrogen where nitrogen has a formal oxidation state of −3. Nitrides are a large class of compounds with a wide range of properties and applications....
(CrN) thin films were deposited by HIPIMS for the first time in February 2001 by A.P. Ehiasarian. The first thorough investigation of films deposited by HIPIMS by TEM
Transmission electron microscopy
Transmission electron microscopy is a microscopy technique whereby a beam of electrons is transmitted through an ultra thin specimen, interacting with the specimen as it passes through...
demonstrated a dense microstructure, free of large scale defects. The films had a high hardness, good corrosion
Corrosion
Corrosion is the disintegration of an engineered material into its constituent atoms due to chemical reactions with its surroundings. In the most common use of the word, this means electrochemical oxidation of metals in reaction with an oxidant such as oxygen...
resistance and low sliding wear
Wear
In materials science, wear is erosion or sideways displacement of material from its "derivative" and original position on a solid surface performed by the action of another surface....
coefficient. This research paved the way to the first industrial upscaling of the technology in January 2004 at Sheffield Hallam University
Sheffield Hallam University
Sheffield Hallam University is a higher education institution in South Yorkshire, England, based on two sites in Sheffield. City Campus is located in the city centre, close to Sheffield railway station, and Collegiate Crescent Campus is about two miles away, adjacent to Ecclesall Road in...
, UK in collaboration with Advanced Converters, Warsaw, Poland (present day Hüttinger Electronics, Poland). The commercialisation of HIPIMS hardware that followed from this made the technology accessible to the wider scientific community and triggered developments in a wide range of areas.
The following materials have, amongst others, been deposited successfully by HIPIMS:
- Corrosion Resistant: CrN/NbNNiobium nitrideNiobium nitride is a compound of niobium and nitrogen with the chemical formula NbN. At low temperatures , niobium nitride becomes a superconductor, and is used in detectors for infrared light.-Uses:...
nanoscale multilayer - Oxidation Resistant: CrAlYN/CrN nanoscale multilayer, Ti-Al-Si-N, Cr-Al-Si-N nanocompositeNanocompositeA nanocomposite is as a multiphase solid material where one of the phases has one, two or three dimensions of less than 100 nanometers , or structures having nano-scale repeat distances between the different phases that make up the material...
- Optical: Ag, TiO2Titanium dioxideTitanium dioxide, also known as titanium oxide or titania, is the naturally occurring oxide of titanium, chemical formula . When used as a pigment, it is called titanium white, Pigment White 6, or CI 77891. Generally it comes in two different forms, rutile and anatase. It has a wide range of...
, ZnO, InSnOIndium tin oxideIndium tin oxide is a solid solution of indium oxide and tin oxide , typically 90% In2O3, 10% SnO2 by weight. It is transparent and colorless in thin layers while in bulk form it is yellowish to grey...
, ZrO2Zirconium dioxideZirconium dioxide , sometimes known as zirconia , is a white crystalline oxide of zirconium. Its most naturally occurring form, with a monoclinic crystalline structure, is the rare mineral baddeleyite. The high temperature cubic crystalline form is rarely found in nature as mineral tazheranite O2...
, CuInGaSe - MAX phases: TiSiC
- Microelectronics: Cu, Ti, TiNTitanium nitrideTitanium nitride is an extremely hard ceramic material, often used as a coating on titanium alloys, steel, carbide, and aluminium components to improve the substrate's surface properties....
, Ta, TaN - Hard Coatings: carbon nitrideBeta carbon nitrideBeta carbon nitride is a material predicted to be harder than diamond.The material was first proposed in 1985 by Marvin Cohen and Amy Liu. Examining the nature of crystalline bonds they theorised that carbon and nitrogen atoms could form a particularly short and strong bond in a stable crystal...
CNx
Industrial application
HIPIMS has been successfully applied for the deposition of thin films in industry. The first HIPIMS coating units appeared on the market in 2006 and were supplied by SVS Vacuum Coating Technologies GmbH.External links
- http://svs-vct.com/
- http://materials.shu.ac.uk/ncpvd
- http://www.ifm.liu.se/plasma/reshppms.html
- http://www.cemecon.de/information/news/hppms__high_plasma_ionisation/index_eng.html
- http://www.melec.de