[Paper Review] An upgraded ultra-high vacuum magnetron-sputtering system for high-versatility and software-controlled deposition

Arnaud le Febvrier, Ludvig Landälv+4 more|arXiv (Cornell University)|Oct 16, 2020

Metal and Thin Film Mechanics31 references86 citations

TL;DR

This paper presents an upgraded ultra-high vacuum (UHV) magnetron sputtering system designed for high versatility in depositing metallic, oxide, nitride, and oxynitride films. The system integrates software-controlled automation via custom LabVIEW software for precise, reproducible process control, including real-time logging, shutter timing, bias voltage application, and coil-enhanced plasma density, enabling complex multilayer and superlattice deposition with full parameter synchronization and programmable sequences through CSV-based layer definition.

ABSTRACT

Magnetron sputtering is a widely used physical vapor deposition technique. Reactive sputtering is used for the deposition of, e.g, oxides, nitrides and carbides. In fundamental research, versatility is essential when designing or upgrading a deposition chamber. Furthermore, automated deposition systems are the norm in industrial production, but relatively uncommon in laboratory-scale systems used primarily for fundamental research. Combining automatization and computerized control with the required versatility for fundamental research constitutes a challenge in designing, developing, and upgrading laboratory deposition systems. The present article provides a detailed description of the design of a lab-scale deposition chamber for magnetron sputtering used for the deposition of metallic, oxide, nitride and oxynitride films with automated controls, dc or pulsed bias, and combined with a coil to enhance the plasma density near the substrate. LabVIEW software (provided as Supplementary Information) has been developed for a high degree of computerized or automated control of hardware and processes control and logging of process details.

Motivation & Objective

• To address the challenge of combining high versatility with automated, computerized control in lab-scale physical vapor deposition systems for fundamental research.
• To enable precise, reproducible deposition of diverse materials—metallic, oxide, nitride, and oxynitride films—under UHV conditions.
• To develop a software-controlled system capable of managing complex deposition sequences, including multilayers and superlattices, with synchronized control of shutters, bias, and plasma enhancement.
• To provide a freely modifiable, open-source LabVIEW software framework for replication and adaptation in other deposition systems.

Proposed method

• The system features a UHV chamber (base pressure < 3.9×10⁻⁷ Pa) made of low-carbon stainless steel, equipped with a load-lock for sample transfer.
• Four magnetron sputtering sources support dc, rf, or pulsed-dc power, enabling deposition of various materials using Ar, O₂, and N₂ gases with mass flow controllers.
• A substrate bias supply and an external coil are used to enhance plasma density and control ion bombardment energy during deposition.
• A custom LabVIEW software interface enables real-time monitoring, logging, and automated control of all process parameters including pressure, gas flow, power, voltage, current, temperature, and arc counts.
• Deposition sequences, including multilayers and superlattices, are programmed via a comma-separated values (CSV) file defining time, shutter status, bias, and coil settings per layer.
• The system includes a quadrupole mass spectrometer for residual gas analysis and real-time monitoring of reactive gas partial pressures during deposition.

Experimental results

Research questions

• RQ1 How can a lab-scale magnetron sputtering system achieve high versatility in depositing metallic, oxide, nitride, and oxynitride films under ultra-high vacuum conditions?
• RQ2 What level of automation and process control can be achieved in a research-grade system using software-based control, and how does it improve reproducibility?
• RQ3 How does substrate rotation and coil-enhanced plasma density affect the uniformity and energy distribution of sputtered species on the substrate?
• RQ4 To what extent can a custom LabVIEW software framework enable complex deposition sequences such as multilayers and superlattices with synchronized control of multiple system components?
• RQ5 Can the integration of real-time logging and parameter synchronization significantly enhance experimental traceability and reproducibility in fundamental materials research?

Key findings

• The system achieves a base pressure below 3.9×10⁻⁷ Pa after baking at 140 °C for 48 hours, ensuring high vacuum integrity.
• Effective pumping speeds of up to 216 l/s were measured at 0.33 Pa (2.5 mTorr) argon pressure, minimizing hysteresis in reactive sputtering processes.
• Substrate rotation reduces deposition inhomogeneity, with particle flux variation decreasing from 50% (non-rotating) to 9% (rotating) across the substrate zone.
• The LabVIEW software enables real-time monitoring of up to six process variables simultaneously, with full data logging and automated control of shutters, bias, and coil power.
• The use of a CSV-based layer definition file allows for unlimited layer sequences and complex parameter combinations, facilitating the deposition of multilayer and superlattice structures.
• The system supports automated target cleaning procedures and synchronized control of multiple components with a 1-second waiting time to ensure timing accuracy across shutters and power supplies.