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12/1/2008 1 PROCESSING OF INTEGRATED CIRCUITS Overview of IC Processing Silicon Processing Lithography Layer Processes Use in IC Fabrication Integrating the Fabrication Steps IC Packaging Integrated circuit (IC) A collection of electronic devices such as transistors, diodes, and resistors that have been fabricated and electrically intraconnected onto a small flat chip of semiconductor material Silicon (Si) most widely used semiconductor material for ICs, due to its combination of properties and low cost Less common semiconductor materials: germanium (Ge) and gallium arsenide (GaAs) Since circuits are fabricated into one solid piece of material, the term solid state electronics is used for these devices Overview of IC Technology An integrated circuit consists of hundreds, thousands, or millions of microscopic electronic devices that have been fabricated and electrically intraconnected on the surface of a silicon chip A chip is a square or rectangular flat plate that is about05 mm (0 020 in) thick and typically 5 to about 0.5 mm (0.020 in) thick and typically 5 to 25 mm (0.2 to 1.0 in) on a side Each electronic device (e.g., transistor) on the chip surface consists of separate layers and regions with different electrical properties combined to perform the particular electronic function of the device Figure 35.1 Cross section of a transistor (specifically, a MOSFET) in an integrated circuit. Approximate size of the device is shown; feature sizes within the device can be less than 1 m with current technology. Packaging of ICs To connect the IC to the outside world, and to protect it from damage, the chip is attached to a lead frame and encapsulated inside a suitable package The package is an enclosure, usually made of plastic or ceramic, that provides mechanical and environmental protection for the chip It includes leads by which the IC can be electrically connected to external circuits Figure 35.2 Packaging of an integrated circuit chip: (a) cutaway view showing the chip attached to a lead frame and encapsulated in a plastic enclosure, and (b) the package as it would appear to a user. This type of package is called a dual in line package (DIP).
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12/1/2008 2 Processing Sequence for Silicon based ICs Silicon processing sand is reduced to very pure silicon and then shaped into wafers IC fabrication processing steps that add, alter, and remove thin layers in selected regions to form electronic devices Lithography is used to define the regions to be processed on wafer surface IC packaging wafer is tested, cut into individual chips, and the chips are encapsulated in an appropriate package Figure 35.3 Sequence of processing steps in the production of integrated circuits: (1) pure silicon is formed from the molten state into an ingot and then sliced into wafers; (2) fabrication of integrated circuits on the wafer surface; and (3) wafer is cut into chips and packaged Clean Rooms Much of the processing of ICs must be carried
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This note was uploaded on 05/05/2011 for the course IE 370 taught by Professor Chunghorng,r during the Spring '08 term at Purdue University-West Lafayette.

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