First Wide Area Scanning Magnetron PVD production tool
developed by R. Demaray as General Manager at Applied Komatsu, 1997.
First Wide Area Scanning Magnetron PVD production tool
developed by R. Demaray as General Manager at Applied Komatsu, 1997.
Thin Films: These days, many of our products depend on vacuum thin films. But few people have any idea what these materials look like, on their surface, or through their thickness. Everything from solar window glass coatings to the thin films that are used to store information magnetically or optically, to solid state semiconductor layers used in thin film transistors or for memory chips, have coatings which are manufactured by different vacuum processes involving chemical vapor or physical vapor deposition.
Quality of Thin Films: What isn’t readily apparent to investors or customers is that these films are not perfect but often have a roughness greater than their thickness and have many kinds of defects that are present in high numbers. A hundred million defects per square centimeter are not unusual. Even some single crystals have that many defects. So it should not be a surprise that a film would have holes or voids or regions with no mechanical adhesion to the substrate, and films on window glass or plastic are worse.
Defects might be ok in a window coating if your eye can’t see them; however, the level of defects in a window coating that are acceptable to the human eye could not be tolerated in a data-recording layer. In turn, the defects in the recording layer, although smaller yet, could not be tolerated in a layer intended to protect a metal film or object from oxidation or corrosion. When a typical thin film is imaged with a scanning electron microscope, or SEM, so that its thickness can be seen from the side or its surface is imaged at the same magnification, it is possible to see the so-called texture of the films. In a fracture cross section, the film breaks along the lines of its defect structure and can clearly show its texture and its larger defect structures.
Other PVD Thin Films: On the upper right side of Figure 1. is an SEM of the fracture cross section of a sputtered film of zirconium oxide made by a standard sputtering process. It looks like it is composed of close packed columns where the larger ones seem to crowd out the smaller ones. To the eye, looking through it on glass, this film is transparent. This is typical of most vacuum deposited oxide films. At a higher temperature, closer to the melting point of a film, it might look like a sun baked mud flat with a smooth surface and mud flat cracks through its thickness.
Defect Free Antropy Thin Films: The large central picture in Figure 1. is a higher resolution TEM, or transmission electron micrograph, which shows a fracture cross section of a Antropy film comprised of an equally high temperature film alloyed of quartz and sapphire. It was deposited by means of the SI bias - pulsed DC process and is fully glassy, amorphous and smooth on an atomic scale. As shown by the x-ray diffraction spots, it has no crystallinity, so they are diffuse circles. If there were any crystallinity, there would be spots in the diffraction circles. So the film made with the Antropy technology is smooth and glass-like on an atomic scale, what is referred to as “amorphous”. It is the first transverse transparent film made by wide area manufacturing. The standard film is not transparent enough to carry light in the film along the surface of the substrate, as it would be scattered out within millimeters. But the Antropy film can carry light many centimeters, as shown by the graph of data, without any detectable loss. Battelle Labs in Columbus Ohio independently measured this data. In electrical or barrier applications, the defects that scatter light also lower the electrical breakdown strength and allow diffusion of water and oxygen or other contaminates. A film without defects can enable profound new electrical, electronic, and mechanical applications. For new applications and products, what is important is that the basic amorphous film can have no electrical or optical defects. Through the film, along the surface of the wafer, it would be equivalent to looking through a piece of glass many inches thick and not being able to notice the glass because it was so clear and transparent. Specialists were amazed that the optical extinction (k) was also immeasurable across the visible spectrum all the way to the UV band edge.