EE141 © Digital Integrated Circuits 2nd Devices 1 Lecture 6. CMOS Device (cont) ECE 407/507
EE141 © Digital Integrated Circuits 2nd Devices 2 Notice Reading Assignment : chapter 1, chapter 3 (finish reading) Both hw1 and lab1 are on the website hw1 due in one week (next Thurs.) Lab1 due in two week (the Thurs. after next )
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EE141 © Digital Integrated Circuits 2nd Devices 6 The Transistor as a Switch
EE141 © Digital Integrated Circuits 2nd Devices 7 The Transistor as a Switch
EE141 © Digital Integrated Circuits 2nd Devices 8 The Transistor as a Switch
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EE141 © Digital Integrated Circuits 2nd Devices 11 C GCB_1 C GCS C GCD
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EE141 © Digital Integrated Circuits 2nd Devices 18 The Sub-Micron MOS Transistor Threshold Variations Subthreshold Conduction Parasitic Resistances
EE141 © Digital Integrated Circuits 2nd Devices 19 Threshold Variations V T L Long-channel threshold LowV DS threshold Threshold as a function of the length (for lowV DS ) Drain-induced barrier lowering (for lowL) V DS V T
EE141 © Digital Integrated Circuits 2nd Devices 20 Sub-Threshold Conduction V GS (V) I D (A) VTVT Linear Exponential Quadratic Typical values for S: mV/decade The Slope Factor S is V GS for I D 2 / I D 1 =10
EE141 © Digital Integrated Circuits 2nd Devices 21 Sub-Threshold I D vs V GS V DS from 0 to 0.5V
EE141 © Digital Integrated Circuits 2nd Devices 22 Sub-Threshold I D vs V DS V GS from 0 to 0.3V
EE141 © Digital Integrated Circuits 2nd Devices 23 Summary of MOSFET Operating Regions Strong Inversion V GS > V T Linear (Resistive) V DS < V DSAT Saturated (Constant Current) V DS V DSAT Weak Inversion (Sub-Threshold) V GS V T Exponential in V GS with linear V DS dependence
EE141 © Digital Integrated Circuits 2nd Devices 24 Parasitic Resistances
EE141 © Digital Integrated Circuits 2nd Devices 25 Future Perspectives 25 nm FINFET MOS transistor
EE141 © Digital Integrated Circuits 2nd Devices 26 New Tech: Silicon On Insulator (SOI) Silicon wafers are highly perfect : critically important for achieving high device yield. But a more radical change may be needed in the material structure, processing method, or device design in order to enhance the circuit performance.
EE141 © Digital Integrated Circuits 2nd Devices 27 Why use SOI Extend the life of traditional silicon technology Boost speed Reduce power consumption Solve some scaling difficulties
EE141 © Digital Integrated Circuits 2nd Devices 28 Transistor crosssection
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EE141 © Digital Integrated Circuits 2nd Devices 30 SOI material structure SOI material structure
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EE141 © Digital Integrated Circuits 2nd Devices 35 Benefits of SOI -performance
EE141 © Digital Integrated Circuits 2nd Devices 36 Benefits of SOI -- power
EE141 © Digital Integrated Circuits 2nd Devices 37 Benefits of SOI – timing
EE141 © Digital Integrated Circuits 2nd Devices 38 SiGe: Silicon Germanium Used to be inefficient in chip production Extremely high frequencies: 60Ghz Very little power usage 70% faster, 35% less power
EE141 © Digital Integrated Circuits 2nd Devices 39 Why SiGe The layer of latticed silicon and germanium added to the chips silicon layer increases the distance between silicon atoms Less force between atoms, easy for electrons to pass by with less resistance IBM suggests combining SiGe and SOI
EE141 © Digital Integrated Circuits 2nd Devices 40 Thermal problem with SiGe Thermal problem with SiGe The diagram above shows the effect of localized self-heating in the emitters (30C for 40mv)