Applications of Sputtered Films

In the fields of microelectronics and optoelectronics, sputtered thin films have been used extensively for:

• Metallization and diffusion barriers in microelectronic circuits (Ref 73, 74, 75)

• Insulating layers in microelectronic circuits

• Thin-film layers in compact disks

• Transparent conducting electrodes

• Thin-film resistors and capacitors

• Piezoelectric transducers

• Amorphous optical films in integrated circuits

• Thin-film lasers

• Memory devices

• High-temperature superconductors

A variety of sputtering techniques can be used in most applications, but rf and magnetron sputtering seem to be most prevalent. Magnetrons are fairly common because they allow very low substrate temperatures. Because most of the above applications are planar in nature, sufficient ion bombardment at the substrate is not an issue. Sputtered thin films are also used extensively in wear-resistant applications such as:

• Decorative coatings on eyeglass frames, watch cases, and other consumer goods (Ref 19, 76)

• Protective coatings on high-speed cutting tools (Ref 77, 78, 79)

• Tribological coatings on bearing surfaces (Ref 80, 81, 82)

• Heat-reflecting optical coatings on architectural glass panels (Ref 83)

• Multilayer dielectric coatings of laser mirrors and filters

• Chromium-base replacements for electrodeposited hard chrome (Ref 84, 85)

Transition metal nitrides, carbides, and oxides such as TiN, TiAlN, CrN, Ta2O3, and Al2O3 are frequently used in these applications because of their extreme hardness, corrosion resistance, attractive colors, and high spectral reflectance. In decorative applications, for instance, TiN-based films can be tailored to produce the color and brightness of gold but with superior scratch resistance at a reduced cost. With the previously described process control methods, various color values can be preselected and reproduced. In magnetron sputtering, substrate temperatures as low as 150 to 220 °C can be maintained throughout the deposition process, and, thus, temperature-sensitive materials such as electroplated brass, die-

cast zinc, and bronze can be used as substrate materials for decorative coatings. Sputtered decorative coatings are usually deposited in thicknesses ranging from 0.2 to 2 pm.

Although electronic and wear-resistant coatings are the two broadest categories of commercially produced sputtered thin films, there are many other applications. For example, sputter-deposited metallic thin films are widely used as moisture and gas-diffusion barrier coatings on polymer films in the packaging industry. The applications for sputter-deposited thin films continue to broaden in scope each year.

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