Bioceramic Coating on Titanium by Physical and Chemical Vapor Deposition - Biological and Biomedical Coatings: Processing and Characterization - page 305

such as Ca-Ti-O and Ca-P-O system films on Ti. Although the deposition temperature of
CVD is generally higher than that of PVD and resulting in the mechanical degradation of
Ti, lowering of the deposition temperature in CVD has been attempted by adopting metal
organic (MO) precursors combined with auxiliary energy by laser.

BioceramicCoatingbyPVD
Sputtering

Sputtering is most widely and commonly employed to manufacture thin films in many
industries. In sputtering, highly accelerated ions, typically Ar + , are emitted to a source
material (target), and then sputtered atoms or clusters are deposited on a substrate to form
thin films.
Radio-frequency (RF) magnetron sputtering is the process in which the Ar + ions forming
plasma by the radiofrequency radiation sputter the target and then deposit the target mate-
rial on the substrate. Figure 7.7 shows a schematic illustration of the RF magnetron sputter-
ing apparatus. The sputtering chamber is evacuated to a total pressure of less than 10 −4 Pa,
and then sputtering gas such as Ar or a mixture of Ar-O 2 is introduced into the chamber
where it reaches a total pressure of several pascals. As shown in Figure 7.8, a permanent
magnet is located behind a target, and the magnetic field forms a closed-loop annular path.
Since the secondary electrons ejected from the target take a cycloidal path, the probability
of ionization of the sputtering gas within the confinement zone increases greatly. (29)
The RF magnetron sputtering process has many advantages: (30)

• High deposition rate
• Ease of sputtering any metal, alloy, or compound
• High-purity films
• High adhesion of films
• Excellent coverage of steps and small features
• Ability to coat low refractory substrates
• Ease of automation
• Uniformity in thickness and roughness on large-area substrates

Chamber

Substrate
holder
Substrate

Heater

MFC
MFC

Ar O 2 Shutter

Plasma

Target Magnet

Vacuum
system
(TMP, RP)

RF Electrode

RF Power

FIGURE 7.7
Schematic illustration of RF magnetron sputtering.