IMPULSE™ - 2kW Pulsed Power Modules for Advanced Magnetron Sputtering

Overview

The Kurt J. Lesker Company^® is the official distributor of the Starfire Industries HIPIMS IMPULSE™ supply is a versatile pulsed power module that converts a conventional DC sputtering system into a fully-functional High-Power Impulse Magnetron Sputtering (HiPIMS) system. The 2kHz-2kW IMPULSE™ is an affordable thin-film coating solution that is ideal for small 1" to 4" cylindrical and linear cathodes. High-performance dense, high-hardness, non-porous films and superior optical coatings for university, industrial and governmental R&D applications are within reach. The design is available with standard afterglow or with a patent pending positive kick option in either a single or dual module configuration all in a 2U rack. The IMPULSE™ is ideal for reactive sputtering and synchronized co-sputtering or substrate timed pulse bias on dielectric and metal sputtering targets.

Features

• Capable of combinations for sequential and parallel pulse firings to achieve the optimal operating environment for your application.
• Easily sputtered metals, like copper and aluminum, can draw high peak currents at lower repetition rate. More difficult metals or dielectrics can be effectively managed at high-repetition rate with lower peak currents.
• Up to 200 A peak current capability for power handling and high deposition rate
• User selectable pulse width, frequency and peak current
• Real-time discharge voltage and current monitoring; integrated power feedback with touch-screen control
• Arc detection and suppression technology
• Precision master/slave module timing for substrate bias or cathode synchronization for co-deposition
• The IMPULSE™ 2-2 retains the synchronization and substrate bias timing capability to selectively choose which ions will implant in the film densification phase. This allows users to tailor the substrate bias energy for metal or dielectric ion implantation while minimizing carrier gas ion effects
• Multiple IMPULSE™ modules can be synchronized for cluster tool operation.
• Available in single or dual module configuration in standard 2U rack enclosure to power multiple magnetron heads, i.e. cluster tools, or a pulsed substrate bias with sub µs timing
• Touch screen interface with direct parameter entry and tactile knob control, plus rear panel RJ-45 and RS-422 serial microcontroller interfaces with external TTL sync pulse and monitor outputs

Process

• Easy way to upgrade existing DC sputtering systems for HiPIMS/HPPMS and reactive capability
• Use your existing DC power supply as the charging supply or bias input*

Dimensional Drawings

Applications

• High-Power Impulse Magnetron Sputtering
• High-Power Pulsed Magnetron Sputtering (HiPIMS/HPPMS)
• Advanced coatings for university, industrial and governmental R&D applications
• Dense, high-hardness materials, non-porous films and superior optical coatings
• Ideal for 2", 3" and 4" circular magnetrons requiring high impulse power and pulse flexibility

DLC Coatings: DLC Coatings(diamond-like carbon coating),is a nanocomposite coating with unique properties of natural diamond low friction, high hardness, and high corrosion resistance.

Recent testing has shown that DLC coatings can be optimized using HIPIMS technology. The higher level of ionized material produced in HIPIMS due to higher plasma densities, enhances the film density and hardness resulting in much higher levels of sp3 orbitals in DLC films.

SEM Images of Carbon Thin Films

500 nm thick Carbon deposited typical DCMS: Shows a grainy, porous film.

1 µm thick Carbon deposited by HIPIMS: Shows a very dense, smooth film structure.

The cross-section on the left is an example of typical DCMS of Copper. On the right shows indication that HiPIMS engenders the ability to collimate the sputtered ions and guide them into aspect features.

High Aspect Ratio Coatings

Coating requirements which involve non-flat substrates with minor or severe trenches. The objective is being to more effectively coat aspect ratio features that typical sputtering is unable to achieve.

Adding A Substrate Bias

A negative substrate bias attracts generated positive ions in the chamber. This enables you to pulse a strategically timed DC bias to choose either to attract the metal sputtered ions or the Argon ions to the substrate.

This technique is ideal in high aspect ratio coating applications.

SEM image of sample with extreme 30:1 aspect ratio features that was coated at the Kurt J. Lesker Company using the HIPIMS process (*Data/Sample provided by Dr. Fred Newman of University of Washington)

Top of via (Green indicates thickness of copper film)

Bottom of via (Green indicates thickness of copper film)

Summary:

Sputtered target atoms that are ionized can potentially be guided into aspect ratio features. Biasing the substrate increases the effectiveness of the HIPIMS process. The effectiveness for the HIPIMS process to be used for aspect ratio coverage is dependent on the material being sputtered since materials differ in sputtered ion to neutral ratios. Initial results from the first attempt are encouraging for full coverage in a 30:1 aspect ratio feature.

Options

• Single and Dual Configurations
• Optional user-adjustable patent pending positive kick pulse that engages after the termination of the main negative pulse to enhance ion transport to the substrate, increase deposition rate and tailor film stress, as well as clearing charge on surfaces for reactive applications-broadening the process envelope.

Single Configuration

Dual Configuration

Patent Pending Positive Kick Pulse: Optional user-adjustable patent pending positive kick pulse that engages after the termination of the main negative pulse to enhance ion transport to the substrate, increase deposition rate and tailor film stress, as well as clearing charge on surfaces for reactive applications-broadening the process envelope.

1. Good For Film Rate: 10-20% compared to conventional HiPIMS
2. Good For Film Quality: Add ion energy to the substrate (up to 200ev) without having to bias the substrate or heat surface. stress relief! ion energy annealing from short impulse burst. has annealing effect to reduce film stress.
3. Good For Reactive Applications: clean oxide and nitride off the anode to mitigate the disappearing anode phenomena. provide return electrons to target surface to "cancel" surface charging to lessen microarc formation.

Short Kick: The positive pulse "reverses" the potential and immediately kicks the metal ions towards the substrate

Give 10-100's ev energy to metal ions entrained in magnetic trap and direct away from sputter gun

Long Kick: Elevates plasma potential positive at substrate allowing argon ions to accelerate into substrate for additional heating & film energy. substrate grounding has a role here

Good for Reactive Sputtering

Electron backflow: electrons go back to the target surface and "charge" oxide and nitride particles on surface for "cleaning" on next pulse

Ion Backflow: ions go to anode for some sputtering of oxides and nitrides to clean electrode to mitigate "disappearing anode" phenomena like pulsed dc but better.

Increases deposition rate and changes stress

Deposition rate increases 15%

KICK Parameter Adjustment (0-200V, time)

What about altering the positive pulse?

Stress Reduction & Film Morphology Change

Morphology also shows Some changes

Pair with upgraded magnetic pack for higher performance TORUS^® PVD tools

Performance

When HIPIMS was first introduced to the market, it was intended to be a technology for providing enhanced film properties to large scale production applications. The supplies were very large and cost prohibitive to the R&D community. However, with the recent release of R&D scale supplies such as the HIPIMS IMPULSE™, HIPIMS technology is being used on a much wider range of applications and the results are nothing less than impressive!

During the pulse, extreme power densities (several of kW/in2) are reached on the target. Due to the high plasma densities a large fraction of sputtered material is ionized, but the time average power remains at an acceptable level as to not damage the sputter target or magnetron sputter cathode

This results in films with higher density, smoother surfaces, higher refractive indexes, modified crystalline structures, enhanced hardness, etc.

The SEM examples below show the differences between films running with HIPIMS and DCMS at the same time average powers and parameters.

(Left) Conventional dcMS copper deposition on silicon on showing rough surface morphology globular microstructure.
(Right)IMPULSE™ 2-2 HiPIMS deposition at same 500W, 10mTorr conditions showing dense, non-porous nanostructure.
While the operating parameters are identical in both films, the quality of the films are completely different and very noticeable.

SEM cross sections from a columnar DC, a dense glassy
HiPIMS coating structure of NiCr²

In DC sputtering, columnar film growth is both expected and acceptable in many sputtering applications. However, there are also a number of applications in which is it not. When smooth, dense film qualities are desired or required, HIPIMS can be an excellent option. Now, with the introduction of smaller scale, R&D size supplies such as the HIPIMS IMPULSE™, HIPIMS technology can be easily and cost effectively added to any existing DC sputtering system

The following SEM images show the film comparison of a CdO sputtering process done with both RF and HIPIMS (reactive sputtering). In this particular application, the customer is depositing CdO for solar, plasmonic sensor, and polaritonic IR device applications. This stems from unique capability to achieve very high mobility and high carrier density in donor-doped CdO. RF sputtering was the preferred method initially due to greater difficulty achieving fully oxidized Cd with a DC plasma

However, after trying the process with HIPIMS, in all comparisons of properties and structure, HIPIMS discharge plasmas achieve a superior structure.

• higher density
• smoother surfaces
• extreme deposition rates
• more complete oxidation
• no anion re-sputtering
• excellent reproducibility
• can run RF magnetron (dopant source) simultaneously

AFM Comparison

RMS = 30nm

90 min deposition
300 nm CdO on sapphire
RF-magnetron

RMS = 1.5nm

10 min deposition
larger crystal size
300 nm CdO on sapphire
HIPIMS

Thick CdO Film Deposition

Plan-view

3 micron thick CdO
Deposition Rate: 60 nm/min
Surface Roughness: 5 nm RMS

X-section

CdO
Dense columnar microstructure
Sapphire

One of the important things to understand with a smaller scale supply is how effectively performance can be scaled up to production level applications. Through some collaboration with the Fraunhofer IST facility, HIPIMS films with the HIPIMS IMPULSE™ were run with Copper and then compared the parameters that are relative to their larger scale supplies.

The results show that the HIPIMS IMPULSE™ supply scales very similarly to what is typical with larger supplies, which is unique in comparison to other results seen with smaller R&D units.

Copper, f=333 Hz, t_on=50 µs

Copper, f=333 Hz, U_charge=550V

High Aspect Ratio coatings are another option being explored with HIPIMS technology. Recent testing has shown HIPIMS to be very effective at coating even some of the most extreme ratios.

SEM images of Carbon coating with HIPIMS (IMPULSE™ power supply)

1µm

2µm

100nm

500nm

SEM Images of Carbon coating with DC magnetron sputtering

2µm

300nm

400nm

500nm