Chapter/Index: Introduction | A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z | Appendix
| The people now believe that the scaling limit to Moore’s law is lithography because of the need for shorter wavelengths of light to pattern the smaller feature sizes. Therefore, materials are now a key constraint in silicon technology. For example, the current density of conductors in ICs can be increased by using copper instead of aluminium. The RC time delays can be minimized using materials with lower dielectric constants instead of SiO2. Leakage in MOS structures can be minimized using materials, with high dielectric constants, between the gate and the silicon channel in FET in stead of SiO2. In integrated circuits (ICs), conductive lines provide electrical interconnection among different parts of the ICs, devices, and the outside. The main applications of metallization are classified by gate, contact, and interconnection. Polysilicon and silicides are commonly applied as gates and interconnects in MOS devices. Aluminum, copper, tungsten, silver, titanium, platinum, gold, and palladium are used as these types of contacts, connections, and/or interconnection to external components. Copper has many good properties such as low resistance and high electromigration endurance. At metal pitches of about 32 and 21 nm, the effective resistivity of damascene Cu wires increases drastically [2] because of: Table 2034a. Properties of some metals commonly used in ICs.
Table 2034b. Metallization selections in ICs.
Figure 2034a. Dependence of recombination lifetime on-metal (Ru, Pt, Cu) concentation in ICs. [1]
[1] H. Aoki, K. Watanabe, T. Iizuka,N. Ishikawa and K. Mori, Ruthenium Film Etching and Cleaning Process Using Cerium Ammonium Nitrate (CAN)-Nitric Acid, Extended Abstracts of the 2001 International Conference on Solid State Devices and Materials, Tokyo, 2001, pp. 20-21.
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