lec26 - 6.012 ­ Microelectronic Devices and Circuits ­...

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Unformatted text preview: 6.012 ­ Microelectronic Devices and Circuits ­ Fall 2005 Lecture 26­1 Lecture 26 ­ 6.012 Wrap­up December 13, 2005 Contents : 1. 6.012 wrap­up Announcements: exam TA review session: December 16, 7:30­9:30 PM, Final exam: December 19, 1:30­4:30 PM, duPont; open book, calculator required; entire subject under examina­ tion but emphasis on lectures #19­26. Final 6.012 ­ Microelectronic Devices and Circuits ­ Fall 2005 Lecture 26­2 1. Wrap up of 6.012 The amazing properties of Si • two types of carriers: electrons and holes – however, can make good electronic devices with just one, i.e. MESFET (Metal­Semiconductor Field­ Effect Transistor), or HEMT (High Electron Mo­ bility Transistor) – but, can’t do complementary logic (i.e. CMOS) without two 6.012 ­ Microelectronic Devices and Circuits ­ Fall 2005 Lecture 26­3 • carrier concentrations can be controlled by addition of dopants – over many orders of magnitude (about 20!) – and in short length scales ( nm range) 37 nm gate length MOSFET from Intel (IEDM ’05). Image removed due to copyright restrictions. 6.012 ­ Microelectronic Devices and Circuits ­ Fall 2005 Lecture 26­4 carrier concentrations can be controlled electrostati­ • cally over many orders of magnitude (easily 10!) 6.012 ­ Microelectronic Devices and Circuits ­ Fall 2005 Lecture 26­5 carriers are fast: • – electrons can cross L = 0 . 1 µm in about: L . 1 µm τ = = 10 7 cm/s = 1 ps v e – high current density: J e = qnv e = 1 . 6 × 10 − 19 C × 10 17 cm − 3 × 10 7 cm/s = 1 . 6 × 10 5 A/cm 2 ⇒ high current drivability to capacitance ratio • extraordinary physical and chemical properties – can control doping over 8 orders of magnitude (p type and n type) – can make very low resistance ohmic contacts – can effectively isolate devices by means of pn junc­ tions, trenches and SOI 6.012 ­ Microelectronic Devices and Circuits ­ Fall 2005 Lecture 26­6 The amazing properties of Si MOSFET source gate body polysilicon gate p p + n + n + n + drain gate oxide inversion layer n channel • ideal properties of Si/SiO...
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lec26 - 6.012 ­ Microelectronic Devices and Circuits ­...

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