lecture21

Lecture21 - 6.720J/3.43J Integrated Microelectronic Devices Spring 2007 Lecture 22-1 Lecture 21 The Si surface and the Metal-Oxide-Semiconductor

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Unformatted text preview: 6.720J/3.43J - Integrated Microelectronic Devices - Spring 2007 Lecture 22-1 Lecture 21 - The Si surface and the Metal-Oxide-Semiconductor Structure (cont.) March 23, 2007 Contents: 1. Ideal MOS structure under zero bias (cont.) 2. Ideal MOS structure under bias Reading assignment: del Alamo, Ch. 8, §§ 8.2 (8.2.3, 8.2.4), 8.3 (8.3.1) Cite as: Jesús del Alamo, course materials for 6.720J Integrated Microelectronic Devices, Spring 2007. MIT OpenCourseWare (http://ocw.mit.edu/), Massachusetts Institute of Technology. Downloaded on [DD Month YYYY]. 6.720J/3.43J - Integrated Microelectronic Devices - Spring 2007 Lecture 22-2 Key questions • What happens if a voltage is applied to the metal with respect to the semiconductor in a MOS structure? • How much voltage needs to be applied to bring the MOS struc- ture to the onset of inversion? • How does the inversion charge evolve with voltage? Cite as: Jesús del Alamo, course materials for 6.720J Integrated Microelectronic Devices, Spring 2007. MIT OpenCourseWare (http://ocw.mit.edu/), Massachusetts Institute of Technology. Downloaded on [DD Month YYYY]. 6.720J/3.43J - Integrated Microelectronic Devices - Spring 2007 Lecture 22-3 1. Ideal MOS structure under zero bias Inversion E o E o E o χ i χ W M E ci s W S E c E F E gi E F E v E vi a) metal, insulator and semiconductor far apart W M E F E o E c E F E o E v W S q φ bi q ϕ p χ s χ i b) metal, insulator and semiconductor in intimate contact Cite as: Jesús del Alamo, course materials for 6.720J Integrated Microelectronic Devices, Spring 2007. MIT OpenCourseWare (http://ocw.mit.edu/), Massachusetts Institute of Technology. Downloaded on [DD Month YYYY]. 6.720J/3.43J - Integrated Microelectronic Devices - Spring 2007 Lecture 22-4 ρ Q g x dmax 0 0 x-x ox -qN A Q i ε ox 0 Q i ε s ε ε s -x ox 0 x dmax x -x ox 0 x dmax x φ φ bi 0 φ sth log p o , n o p o n o N A n i 2 N A -x ox 0 x dmax x q φ sth E c E F E v Q s = Q d + Q i Cite as: Jesús del Alamo, course materials for 6.720J Integrated Microelectronic Devices, Spring 2007. MIT OpenCourseWare (http://ocw.mit.edu/), Massachusetts Institute of Technology. Downloaded on [DD Month YYYY]. 6.720J/3.43J - Integrated Microelectronic Devices - Spring 2007 Lecture 22-5 Do sheet-charge approximation : inversion layer much thinner than any other vertical dimensions of the problem. Two consequences: 1. φ s depends on Q d but is independent of Q i ( φ does not change while crossing a sheet of charge): Q d = − qN A x d − 2 s qN A φ s [same relationship as in depletion] 2. φ s in inversion rather insensitive to actual value of W M : φ s φ sth φ sth is surface potential at threshold Cite as: Jesús del Alamo, course materials for 6.720J Integrated Microelectronic Devices, Spring 2007....
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This note was uploaded on 09/24/2010 for the course EECS 6.720J taught by Professor Jesúsdelalamo during the Spring '07 term at MIT.

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Lecture21 - 6.720J/3.43J Integrated Microelectronic Devices Spring 2007 Lecture 22-1 Lecture 21 The Si surface and the Metal-Oxide-Semiconductor

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