Wafer | Wafer
Key Words: microchip, integrated circuit (IC), silicon chip, wafer loader, stepper, front end wafer fabrication, back-end wafer fabrication
Definition:A thin, circular slice of semiconductor material from which semiconductor / micro chips are made
Wafers are made from semiconductor material typically monocrystalline silicon (or for some applications, compound materials such as gallium arsenide, indium phosphide, cadmium telluride, silicon carbide), which are grown and surface-ground to produce cylindrical shaped ingots or 'boules'. The diameter of the final boule determines the diameter of the wafer. Wafers are manufactured in a variety of diameters, typically 100, 125, 150mm, 200mm and 300mm. Boules are then cut into thin slices (in the region of 0.25 - 300 mm depending on the material and application) and polished on one or both sides to create a uniform optically smooth flat surface. The wafers are then ready to be made into semiconductor chips (also termed integrated circuits (ICs) or simply 'chips'). Microscopy is an important quality control tool in wafer manufacture and can be used to detect and /or measure contaminant particles and defects, the presence of surface metals, oxidation defects, flatness and dimensions. Microscopy can also be used as a diagnostic tool to determine the reasons behind wafer failures such as cracking and breakage.
Wafers are used in the manufacture of electronic integrated circuits for a wide range of uses in, for example, military and aerospace, medical instruments, consumer goods, automotive, and communications fields. Wafer and chip fabrication are central to applications such as lab-on-a-chip and nanotechnology devices.
A variety of microscope systems have been designed for wafer and chip inspection and measurement. Key imaging techniques include brightfield, darkfield, reflected light, DIC, fluorescence and confocal techniques. Manual handling and contamination must be avoided to prevent wafer damage. Inspection and measuring microscopes are usually accompanied by a wafer loader that robotically positions the wafer for examination.
Key equipment includes the Eclipse LV150 series modular reflected light microscope for 150mm wafer inspection, the Eclipse L200 series for 200mm wafers, and L300 series for 300mm wafers. These may be configured with NWL-641 and NWL-860 wafer loaders capable of handling 100-150 mm and 150 and 200mm wafers respectively. DART semiconductor wafer inspection software offers features such as image archiving, defect review, post probe review and online communications.