Hot filament and hot wire CVD processes

The precipitation of polycrystalline diamond films using hot-filament chemical vapour deposition (CVD, HFCVD) is a core competence of the Fraunhofer Institute for Surface Engineering and Thin Films IST. Fully automated HFCVD systems developed at Fraunhofer IST are suitable for coating surfaces up to half a square meter. Processes and systems are also available for the diamond coating of three-dimensional base bodies and for interior diamond coating. Diamond layers with various modifications, for instance with a rough or smooth surface or also as electrically conductive films, are available for different applications. We offer our customers and partners the following services:

Development of substrate or base body

  • Design and material selection according to coating requirements
  • Support for procurement of base bodies

Film development

  • Development of new, application-oriented coating systems
  • Combination with additional PVD or CVD thin films as interlayer or toplayer

Process development

  • Adaption to base body geometry (3D as well as inside geometry) and up-scaling
  • Economical optimization by increasing batch volume and / or high-rate processes
  • Prototypes and small batches for application tests
  • Simulation for process optimization (e. g. film thickness homogeneity, substrate position, reactor concept)

Analytics and quality assurance

  • Measurement of chemical and physical film properties
  • Spatially-resolved measurement of film thickness distribution and coating adhesion
  • Application-specific characterization methods, also in cooperation with partners

Technology transfer

  • Development of customized coating solutions
  • Process transfer to clients or to coating enterprises
  • Design of hot-filament CVD components (e. g. filament holders, substrate cooling)
  • Support for design, procurement and implementation of hot-filament CVD reactors
  • Support for implementation of processes for substrate pretreatment, e. g. finishing, cleaning, seeding
  • Literature, patent and market research, studies, trainings

Hot filament CVD with diamond

Hot filament CVD (chemical vapour deposition) is an established coating method for diamond films.

The technology and its benefits:

  • Chemical precipitation of films from the gas phase (chemical vapour deposition, CVD) following activation of the reactive gas on hot filaments
  • Development of coating processes and systems at Fraunhofer IST
  • Large-scale surface coating (500 x 1000 mm2) with polycrystalline diamond films
  • Diamond coating of three-dimensional base bodies and interior diamond coating
  • Variety of coating modifications adapted to the respective applications

Possible substrate materials: hard metals, silicon, high-melting metals, silicon carbide, silicon nitride, graphite


Hot wire CVD of silicon-based films

Hot filament CVD also has a number of advantages over proven plasma-assisted coating methods for the production of silicon-based films:

The technology and its benefits

  • Chemical precipitation of films from the gas phase (chemical vapour deposition, CVD) following activation of the reactive gas on hot filaments
  • High gas yields
  • High coating rates
  • Straightforward systems technology
  • Readily scalable to coating large areas
  • Gentle coating process with no damage to the substrate, growing layer through high-energy particle bombardment
  • Excellent energy efficiency
  • Low total cost of ownership

Film types

  • Amorphous and microcrystalline silicon (a-Si:H, μc-Si:H); intrinsic and doped films
  • Silicon nitride (SiNx:H)
  • Silicon carbide (SiCx:H)
  • Silicon-germanium alloys (SiGex:H)


  • Absorber layers for thin film photovoltaics
  • Anti-reflection and passivation films for monocrystalline and multicrystalline silicon solar cells
  • Thin film transistors (TFT) for displays
  • Films for microelectronics and microsystems
  • Barrier layers and corrosion protection
  • Transparent scratch protection
  • Gentle etching process with atomic hydrogen