Sputtering process, electroplating

More specifically, metals can be deposited either by electroplating, evaporation, or sputtering processes. Commonly used metals include gold, nickel, aluminum, chromium, titanium, tungsten, platinum and silver. 

Schematic of the Si-nMEA fabrication process (a) sputter Au layer on double-side polished wafer (b) pattern Au layer with liftoff process (c) spincoat and cure a polyimide layer (d) perform the double-sided photolithography to pattern etch pits (e) etch Si in ICP-DRIE to form Au/Si electrode (f) dice the wafer into a single die (g) RIE etch the polyimide layer with a shadow mask to expose current collecting region (h) electroplate Pt black on Au layer (i) sandwich both electrodes with Nafion 112 in a hot-press bonder. (Reprinted from J. Yeom et al. Sensors Actuators B107 (2005) 882-891. With permission from Elsevier.)...

Deposition and patterning of the bottom magnetic pole follow. The pole is usually electroplated with a through-photoresist window frame mask to a thickness level of 2 to 4 fim. Note that whereas the magnetic pole is made into a pancake shape to increase the head efficiency, it is the narrow p>ole tip s dimension that determines the narrow track width. As stated, the widely used Co-based alloy magnetic poles are elec-trodeposited (wet process). Nanocrystalline FeN-based alloys are sputter-deposited in a vacuum chamber (dry process). 

In general, for the deposition of thin films used in microelectronics, low-pressure processes, such as sputtering and low-pressure chemical vapor deposition (LP CVD), are preferred over the older, conventional chemical methods such as electroplating because deposition from an aqueous solution produces poorer quality films. On the other hand electrochemical and electroless metal deposition from solution are gaining renewed interest with micromachinists because of their emerging importance to LIGA. 

Copper can be electroplated onto the substrate in two techniques. In the first process, as shown in Figure 8.25a, an adhesion or seed layer is deposited on the ceramic. This adhesion layer can be thin film, either sputtered or evaporated, thick film, or refractory metallization. A sputtered or evaporated gold layer is deposited on top of the seed layer for thin-film metallization. Copper is then electroplated to the required thickness. This is followed by electroplated nickel and an optional gold electroplate. Figure 8.26 shows the buildup of plated copper metallization. 

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