Photolithography is the transfer of a pattern from a mask to a wafer, using light to effect the transfer.
Diffusion is the uniform distribution of impurity atoms (dopants) into a arrangement of atoms, in a silicon crystal, in a wafer. The purpose of introducing impurities is to change the electrical characteristics of the silicon crystal to make it either P-type silicon or N-type silicon.
Sputtering and evaporating are non chemical methods of depositing thin films of material, usually metals, onto a wafer. Sputtering is accomplished by ionizing Argon gas into a plasma (a collection of charged particles containing about equal numbers of positive ions and electrons and exhibiting some properties of a gas but differing from a gas in being a good conductor of electricity and in being affected by a magnetic field, whew..) and directing the plasma against a metallic target which may contain the aluminum, gold, or some other material to be deposited. The plasma causes some of the material to break off, or sputter when it is directed against a silicon wafer. The material is then deposited onto the surface of the wafer. The controlled growth on a crystalline substrate of a crystalline layer is called an epilayer. In "homo-epitaxy" (e.g., silicon layers on a silicon substrate) the epilayer exactly duplicates the properties and crystal structure of the substrate. In "hetero-epitaxy" (e.g., silicon on sapphire) the deposited epilayer is a different material with a different crystalline structure than that of the substrate.
Chemical Vapor Deposition is a gaseous process that deposits insulating films or metal onto a wafer at elevated temperature. Often reduced pressure is used to promote the chemical reaction.
Ion implantation is a method for adding dopants to semiconductor material. Charged atoms (ions) of elements such as boron, phosphorus or arsenic are accelerated by an electric field into the semiconductor material. This is used for very shallow (<1µm) distributions of dopants in a semiconductor. Ion implantation is usually done at room temperature, with the resulting
implantation-induced lattice damage is removed by annealing (combining with complementary nucleic acid by a process of heating and cooling ) at temperatures of approximately 700 degrees Celsius (C). This process is more precise than the diffusion doping method. By repeating these steps over and over again the components of the circuit ( which may be one of: diodes, transistors, resistors, and capacitors) are embedded internally in the circuit in a number of layers of semiconductor material. This layering of components on a single piece of silicon is Jack Kilby’s revolutionary invention. The drawing on the left depicts the fundamental idea of layering electrical components, much like a series of freeway overpasses. Figure one shows the global consumption of IC’s in the major markets. Note that over the years the growth is growing hugely to expectedly over 200 billion in the year 2000. Also notice the huge share enjoyed by the Americas. Next we move on to the specifics of the above mentioned processes involved in the manufacture of an IC. The first step is photolithography.
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