Thin Films for Microelectronics and Photonics: Physics, Mechanics, Characterization, and Reliability
David T. Read, Alex Volinsky
Thin films of various types are a key component of modern microelectronic and photonic products. Conducting films form the interconnect layers in all chips, and dielectric films provide electrical insulation. With silicon-on-insulator (SOI) and strained silicon, semiconductor films have entered commercial design practice. The term thin films as used here refers to material layers deposited by vapor- or electrodeposition, with thicknesses too small to permit characterization by conventional mechanical testing procedures for bulk materials as described in, e.g., ASTM Standards. Accordingly, our upper limit of thickness is taken as around 20 micrometers. Layers in this thickness range formed by other special processes, like SOI (silicon on insulator) layers, also fall outside the standard mechanical test methods, and require thin-film characterization methods. Copper traces within multi-chip packages may be thicker than the definition given above, but some package designs include films within the present scope. Interconnect layers on die are included in a book on packaging because these layers are often considered to be ¿Level 0 packaging¿, since they are part of the packaging chain that connects the active devices to the outside environment electrically, mechanically, and thermally. The relatively new field of micro electro mechanical systems (MEMS) utilizes semiconductor fabrication techniques, especially lithographic patterning, to produce devices with moving parts and mechanical functions. Commercially important examples include accelerometers, used to trigger the deployment of automotive air bags, and pressure sensors. More recent examples are the moveable mirrors used by Lucent, in optical switches, and Texas Instruments, in Digital Light Processor (TM) systems. Thin films of a material set different from those in microelectronic devices are used here, often including polycrystalline silicon (polySi), designed for mechanical functions. The dimensions of films commonly used in microelectronic products have progressed well into the nanoscale at present, and MEMS technology is evolving the ability to produce nano electro mechanical systems (NEMS). The elements of these products that are well below 1 micrometer in thickness challenge the current leading edge of mechanical characterization of thin films.
and Volinsky, A.
Thin Films for Microelectronics and Photonics: Physics, Mechanics, Characterization, and Reliability, Kluwer, , [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=50201
(Accessed December 8, 2023)