Mumbai University > Electronics Engineering > Sem 8 > MEMS Technology

Marks: 5M

• For basic electrical interconnections, aluminum (usually with a few percentsilicon and perhaps copper) is most common and is relatively easy to deposit by sputtering, but its operation is limited to noncorrosive environments and to temperatures below 300ºC.
• For higher temperatures and harsher environments, gold, titanium, and tungsten are substitutes.
• Aluminum tends to anneal over time and with temperature, causing changes in its intrinsic stresses.
• As a result, it is typically located away from stress- or strain-sensing elements.
• Aluminum is a good light reflector in the visible, and gold excels in the infrared.
• Platinum and palladium are two very stable materials for electrochemistry, though their fabrication entails some added complexity.
• Gold, platinum, and iridium are good choices for microelectrodes, used in electrochemistry and in sensing biopotentials.
• Silver is also useful in electrochemistry. Chromium, titanium, and titanium-tungsten are frequently used as very thin (5–20 nm) adhesion layers for metals that have poor adhesion to silicon, silicon dioxide, and silicon nitride.

Table 2.3 List of Selected Metals That Can Be Deposited As Thin Films (Up to a Few m in Thickness) withCorresponding Electrical Resistivities and Typical Areas of Application