Nano Science (Lec 9 Transistor Moore Law)

Nano Science (Lec 9 Transistor Moore Law) - MAE 287/EE 257...

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MAE 287/EE 257 1
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1822 Mechanical Computer, UK 200 AD “Saun - pan” China 1943, ENIAC, US 3000 BC Sand abacus Babylonia 1948 Transistor, US 2
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Cost per Transistor 5
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Switches are required in telephone communication in Bell Company. "Mr. Watson, come here. I want you.“ -Bell "It will take me five days to get there now!" -Watson Shockley’s idea of field effect device developed in Bell Lab. 6
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Bardeen’s “surface state” explanation of why Shockley’s idea failed Bardeen and Brattain’s point contact transistor 7
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A FET has four terminals, which are known as the gate , drain , source and s ubstrate . Electrons (or holes) can flow from the source toward the drain by an applied a source- drain voltage. This gate permits electrons to flow through or blocks their passage by creating or eliminating a channel between the source and drain. The FET channel is doped semiconductor, and the drain and source may be doped of opposite type to the channel. The Metal–Oxide–Semiconductor (MOS) FET utilizes an insulator (typically SiO 2 ) between the gate and the channel. 9
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A dopant is an impurity element added to a crystal or semiconductor lattice in low concentrations in order to alter the optical/electrical properties of the semiconductor. The process of introducing dopants into a semiconductor is called doping. An electron donor is a dopant that generates electrons. An acceptor is a dopant that generates holes. Substituting a silicon atom in a silicon crystal (top) with a boron (bottom-left) or phosphorous (bottom-right) atom leaves a hole or electron that is relatively free to move around the crystal . 10
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To study the dopant in semiconductor, the complex Schrodinger’s Equation, 2 2 2 E V m is reduced simply to ) ( r 4 e 2 0 0 2 * 2 E E m  We can treat donor atom by using a hydrogen-like model. The donor atom consists of a positively charged ion and an electron with an effective mass m*, just like the proton and electron in a hydrogen atom. 11
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The ionization energy for electron, E c - E d , can be estimated by the electron energy in a Hydrogen atom, yielding: Where m e is the mass of free electron, is the effective mass of electron, and is the relative dielectric constant of the semiconductor. * 2 13.6 eV e cd e m EE m  12 * e m
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a) An electron bound to a donor ion and b) a hole bounded to a acceptor. Ionization of a) a shallow donor and b) a shallow acceptor * 2 * 2 For eletron generated by donor: 13.6 eV For hole generated by acceptor: e cd e h av e m EE m m m  13
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Boron, arsenic, phosphorus, antimony, among other substances, are commonly used dopants in the Si semiconductor industry. 14
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At absolute zero temperature, the Fermi energy level is the highest occupied energy level, that is, all energy levels up to the Fermi level are occupied by electrons.
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This note was uploaded on 04/17/2011 for the course MAE 287 taught by Professor Yongchen during the Winter '11 term at UCLA.

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Nano Science (Lec 9 Transistor Moore Law) - MAE 287/EE 257...

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