HiPIMS
High Power Impulse Magnetron Sputtering (HiPIMS) is a newly developed PVD technology for adhesion enhancement pretreatment and deposition of high density, high performance thin films. It is characterised by a very high pulse power density (up to 3 kWcm-2) at very low duty cycles <5%.
The enhanced power density input in the discharge promotes the ionisation of sputtered material from the target and yields an increased instantaneous plasma density. The use of ionised sputtered target material from the plasma phase is an advantage to a number of applications such as substrate pre-treatment to provide crystalline coating-substrate interface with high adhesion and filling of trenches of semiconductor devices.
The typical characteristics of HiPIMS plasma are:
Peak power ~ kW/cm2
Average power ~ W/cm2
Frequency ~ 10-1000 Hz
Pulse width ~ 10-500 μs
Typical discharge voltage and current waveforms are shown in the picture on the right.
It can be seen that the applied voltage to the magnetron source lasts for very short period of time (~50μs). However, the amount of transferred energy is enough to sustain the plasma until the next pulse.
The introduction of pulsing dramatically changes the energetics of the plasma discharge. The plasma density rises to ~1x1019m-3 compared to ~1x1016m-3 during conventional sputtering. Such increase in plasma density results in increased probability of ionising collisions, where sputtered material is ionised alongside process gas atoms. Some publications indicate that the fraction of ionised sputtered material reaches as high as 90% compared to conventional magnetron sputtering.
The OES spectrum of Ti plasma generated by HiPIMS clearly shows this trend. (The image is reproduced from J. Bohlmark et al., J. Vac. Sci. Technol. A 23, 18 (2005))
| Parameter | HiPIMS | DC Sputtering |
|---|---|---|
| Peak Power Density | 103 Wcm-2 | 1 Wcm-2 |
| Average Power Density | 1 Wcm-2 | 1 Wcm-2 |
| Current Density | 1-103 Acm-2 | 0.01-0.1 Acm-2 |
| Discharge Voltage | 500-1000 V | 500 V |
| Process Gas Pressure | 10-3-10-2 Torr | 10-3-10-2 Torr |
| Magnetic Field Strength | 0.010-0.100 T | 0.010-0.100 T |
| Electron Density | 1018-1019 m-3 | 1016 m-3 |
| Electron Temperature | 1-5 eV | 1-7 eV |
| Degree of Metal Ionisation | 30-100 % | <5 % |
| Ion energy (average for metal ions) | 20 eV | 5 eV |
In addition to increased number of ions, HiPIMS plasma generates ions with energies in the range of 50 eV to 100 eV (compared to only about 2 eV to 10 eV in conventional sputtering). These high energy ions transfer their energy to the coating as it grows, creating very dense coatings. Coatings deposited using HiPIMS do not have the porosity and columnar features typically found in coatings deposited using conventional sputtering techniques.
Ion irradiation
↓
Interruption of columnar growth and re-nucleation
↓
Featureless morphology
The control of ion energy allows the operator to control the growing films over their phase composition, microstructure, as well as mechanical and optical properties. For example, HiPIMS coatings tend to be under compressive stress. The compressive film stress level is controllable by changing the peak power density, since the ion energy scales with peak power.
We supply fully operational UHV deposition sputter system from our QPrep series range to conduct research projects utilising HiPIMS technology. The system features multiple magnetron sputter sources (2-4"), which are powered with DC and HiPIMS power supplies (HiPSTER 1 and HiPSTER 6).
The QPrep system is an ideal instrument not just for creating coatings with HiPIMS, but also for research of plasma discharge conditions influencing the properties of the deposited thin films. The chamber is equipped with multiple ports for installation of various plasma diagnostic techniques.
We source our HiPIMS power supply from Ionautics, which deliver the latest technological developments in HIPIMS sputtering.
The HiPSTER unit is designed to generate a robust and repeatable HiPIMS process, also in reactive mode. This means stable operation with constant voltage throughout the whole discharge pulse without any unwanted oscillations. The HiPSTER integrates with your existing DC power supplies. This is also a cost-efficient way to true HiPIMS.
HiPSTER Features:
- Tested for a full range of magnetrons and processes (incl. reactive HiPIMS) at the Division of Plasma & Coatings Physics, Linköping University
- Stable and robust discharge process (constant voltage and no unwanted oscillations)
- Possibility to externally trigger and control in master-slave configuration (multiple power supplies)
- New switching technology allowing HiPIMS pulsing frequencies up to 2 kHz
- Tested using a wide range of magnetrons and processes (incl. reactive HiPIMS)
- Unique feedback system allowing process regulation by controlling the pulse current
- Real-time information on the discharge pulse voltage and current
- Allows the addition of Ionautics' superposition technology for HiPIMS and DC
HiPSTER Specifications:
The recently developed ultra-fast HiPIMS power supply (by Ionautics) is designed to meet the needs of future HiPIMS processes. While the 1kW HiPSTER unit is ideally suitable for small size sputter sources used in R&D departments and academia, the 6 kW HiPSTER addressed the needs towards the more industrial like applications:
| HiPSTER 1 | HiPSTER 6 | |
|---|---|---|
| Output Average Power | 1 kW | 6 kW |
| Output Peak Voltage | 1 kV | 1 kV |
| Output Peak Current | 100 A | 600 A |
| Regulation Modes | Voltage, Current, Power, Pulse current | Voltage, Current, |
| Pulse Frequency | 1 to 10.000Hz | 1 to 2.000Hz |
| Pulse Duration | 2μs to 1000 µs | 2 µs to 1000 µs |
| Arc control: reaction time | < 2 µs | < 2 µs |
HiPSTER DC Supplies:
HiPSTER 1 DCPSU and HiPSTER 6 DCPSU are suitable DC power supplies for both HiPSTER pulsing units with the following specifications:
| HiPSTER 1 DCPSU | HiPSTER 6 DCPSU | |
|---|---|---|
| Maximum Power | 1.2 kW | 8 kW |
| Maximum Voltage | -1 kV | -1 kV |
| Maximum Current | 1.2 A | 6 A |
HiPSTER DCPSU Features:
- Optimized DC driving unit for HiPSTER 1/HiPSTER 6 supply
- Low storage energy
- Voltage & current outputs continuously adjustable from 0 to 100%
- Voltage & current setting & monitoring from front panel or remote interface
- High reliability & efficiency
- High precision regulation
- Protection against arcs, overloads, short circuits & over temperature
HiPIMS technology opens new opportunity for the deposition of coatings with improved performance in corrosion resistance, film adhesion, oxidation resistance, optical properties, hardness etc. We can help in "tuning" of the HiPIMS process parameters to achieve desired coating properties.
Together with Ionautics we offer consulting services, which include:
- Understanding the basic routes to generate plasma by HiPIMS
- Characterisation of HiPIMS systems: electrical data and plasma diagnostics
- Practical guidance to implementation and optimisation of metal as well as reactive HiPIMS processes
- Set up and initiation of a HiPIMS process
- Implementation and/or optimisation of coating recipes
The coating recipes are:
DLC coatings
- Film density reaching to 2.8g/cm3 (comparable to that obtained from PLD)
- H-content not exceeding 10% (i.e. below the threshold for hydrogenated-DLC)
- More than 50GPa film hardness (on Si substrates)
- Film density and sp3 bond fraction tailoring (without even changing the external/applied bias)
ITO coatings
- Room temperature process
- Proven better coverage of complex-shaped surfaces: coat nano-structures
- Decreased lateral resistivity by decreased intercolumnar porosity
- Decreased surface roughness
Diffusion barriers
- Good coverage even on rough substrate materials such as steel
- Flexible choice of material: Ta, TaN, ZrN etc.
- Phase-tailoring (such as achieving alfa-Ta at room) leads to improved performance
Hard coatings
- Exceptionally dense coatings
- Phase-tailoring (α-Al2O3 achieved at ~500°C) leads to improved performance
- Good coverage even on rough substrate materials such as steel
3D coatings
- Uniform film coverage on complex shaped substrates
The HiPIMS deposited coatings were approximately 15% denser compared to the DC sputter deposited coatings. This could be attributed to the increased metal ion bombardment commonly seen in HiPIMS discharges. The DCMS deposited sample exhibits a porous microstructure and rough surface, whereas the HiPIMS deposited sample exhibits a less pronounced columnar microstructure and a smooth surface.
Mantis Deposition Ltd.
Unit 2, at Thame 40, Jane Morbey Road, Thame
Oxfordshire OX9 3RR
United Kingdom
Tel: +44 (0)1844 260160
Fax: +44 (0)1844 217349
E-Mail: sales@mantis-sigma.com
Web: www.mantisdeposition.com/
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