Introduction

THE PROPERTIES of atomistically deposited films depend strongly on the material being deposited, the substrate surface chemistry and morphology, the surface preparation process, and the details of the deposition process and the deposition parameters. The origin of the unique properties of physical vapor deposition (PVD) film can be understood by understanding the film formation process.

The formation of a useful and commercially attractive engineered surface using any PVD process (vacuum deposition, sputter deposition, or ion plating) involves several stages:

1. Choice of the substrate ("real surface") and development of an appropriate surface preparation process

2. Selection of the film material(s) to produce the surface properties required

3. Choice of the PVD process to provide reproducible properties, compatibility with subsequent processing, and long-term stability

4. Development of the fabrication process parameters, parameter limits, and the monitoring/control techniques

5. Development of appropriate characterization techniques to determine the film properties and stability of the product

6. Creation of written specifications and manufacturing processing instructions to cover the substrate material, surface preparation, deposition process, and characterization procedures

The properties of a film of a material formed by any PVD process depends on four factors:

• Substrate surface condition--e.g., surface morphology (roughness, inclusions, particulate contamination), surface chemistry (surface composition, contaminants), mechanical properties, surface flaws, outgassing, preferential nucleation sites, and the stability of the surface

• Details of the deposition process and system geometry--e.g., angle-of-incidence distribution of the depositing adatom flux, substrate temperature, deposition rate, gaseous contamination, and concurrent energetic particle bombardment (flux, particle mass, energy)

• Details of film growth on the substrate surface--e.g., substrate temperature, nucleation, interface formation, interfacial flaw generation, energy input to the growing film, surface mobility of the depositing adatoms, growth morphology of the film, gas entrapment, reaction with deposition ambient (including reactive deposition processes), and changes in the film properties during deposition • Postdeposition processing and reactions--e.g., reaction of film surface with the ambient, thermal or mechanical cycling, corrosion, interfacial degradation, burnishing of soft surfaces, shot peening, and overcoating ("topcoat")

In order for the film to have reproducible properties, each of these factors must be reproducible.

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