MIT 6 720J - The Short Metal-Oxide-Semiconductor Field-Effect Transistor

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6.720J/3.43J - Integrated Microelectronic Devices - Spring 2007 Lecture 33-1 Lecture 33 - The ”Short” Metal-Oxide-Semiconductor Field-Effect Transistor (cont.) April 30, 2007 Contents: 1. MOSFET scaling (cont.) 2. Evolution of MOSFET design 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 33-2 Key questions • How has MOSFET scaling been taking place? • Are there fundamental limits to MOSFET scaling? • How far will MOSFET scaling go? 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 33-3 1. Scaling (cont.) Scaling goal: extract maximum performance from each generation (maximize Ion), for a given amount of: • short-channel effects (DIBL), and off-current • To preserve electrostatic integrity, scaling has proceeded in a har-monious way: L ( ), W ( ), xox ( ), NA ( ), xj ( ), and VDD ( ).↓ ↓↓ ↑ ↓ ↓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].Illustration 6.720J/3.43J - Integrated Microelectronic Devices - Spring 2007 Lecture 33-4 of key trade-offs:• Ion vs. Ioff 1E-08 1E-07 1E-06 1E-05 1E-04 1E-03 1E-02 1E-01 I off (µµA/µµm) MIT SSR III CMOS Technology Vdd=2 V 0 200 400 600 800 Ion (µµA/µµm) 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 33-5 • Ion vs. DIB L 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 33-6 � Limits to scaling The New York Times (Oct. 9, 1999) 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]. Text removed due to copyright restrictions.Markoff, John. "Chip Progress Forecast to Hit a Big Barrier."The New York Times (October 9, 1999).6.720J/3.43J - Integrated Microelectronic Devices - Spring 2007 Lecture 33-7 Four kinds of limits: • Thermodynamics: doping concentration in source and drain • Physics: tunneling through gate oxide • Statistics: statistical fluctuation of body doping • Economics: factory cost tunneling through gate oxide in source and drain in body doping source gate drain doping concentration � statistical fluctuations � 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 33-8 � Economics: factory cost also follows Moore’s law! New factories cost well in excess of $1B! 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 33-9 � Physics: tunneling through gate oxide (most severe limit) • Oxide’s thickness limit when: Igate � Ioff @ VDD � 1 V, Toper(� 100oC) • Translates to limiting gate current: Igate(25oC) � 100 pA • Limiting gate current density: Ioff (100oC) Ioff (25oC) A � 0.1 µm×0.1 µm =10−10 cm 2 ⇒ Jgate(25oC) � 1 A/cm2 • Limiting xox � 1.6 nm ⇒ L ∼ 35 − 50 nm • Solution: high-dielectric constant gate insulator 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]. Figure 13 on p. 491 in: Taur, Y., et al. "CMOS Scaling into the Nanometer Regime."Proceedings of the IEEE 85, no. 4 (1997): 486-504. © 1997 IEEE.6.720J/3.43J - Integrated Microelectronic Devices - Spring 2007 Lecture 33-10 Current wisdom for limiting bulk CMOS (with nitrided gate oxides): xox � 1.2 nm Leff ∼ 25 − 35 nm⇒ but... unclear if industry will do it (there are better options). � What does this mean? Arno Penzias [1997]: ”We can look forward to a million-fold in-crease in the power of microelectronics”. 10X transistor size reduction ⇒ ⇒ 100X device density ⇒ 100X circuit speed ⇒ 100X surprise 106X TOTAL ⇒� To go beyond this, need: • new materials that squeeze more performance out of existing device architecture – new channel materials: strained Si, Si/SiGe heterostructores – new gate insulators: high-K dielectric, such as HfO – new gate conductors: metal gate, such fully silicided gate • new device architecture (SOI, double gate, trigate) to improve electrostatic integrity 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 33-11 2. Evolution of MOSFET design • PMOS with metal gate: Al gate p+p+ n circa∼early 70’s L ∼ 20 µm xox ∼ 1000˚A xj ∼ 3 µm VDD =12 V Main point: Na+ contamination made NMOS devices to have too negative a threshold voltage Cite as: Jesús del Alamo, course materials for 6.720J Integrated Microelectronic Devices, Spring 2007. MIT


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MIT 6 720J - The Short Metal-Oxide-Semiconductor Field-Effect Transistor

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