Part II: The MOS Transistor Technology J. SÉE johann.see@ief.u-psud.fr 2004/2005
Lecture plan Towards the nanotechnologies... data storage The data processing through the ages MOS transistor in logic-gates gates The microelectronics of today : MOSFET s chronicle of a death foretold? The possible alternatives Coulomb blockade for the nanoelectronics
The numerical integrated circuit star The MOSFET transistor
The MOSFET transistor : operating principle Metal-Oxide-Semiconductor Field Effect Transistor Gate L G e ox Source P Oxide Drain P X j Substrate N
+ The MOSFET transistor : operating principle S ZCE 0>V GS >V T + + + + + - - - - + G + + + + + D S 0>V T>VGS + + + + G ------- + + + + D B V DS =0 1- The electrons are pushed away to the bottom of the substrate B V DS =0 2- A conducting hole chanel is formed between source and drain
+ + + + The MOSFET transistor : operating principle S 0>V T>VGS G ------- Courant I D D I D current + + + + B 3- Movement of holes : I D current starts to flow V DS <0
The MOSFET transistor : operating principle Another way to see the transistor... mobile barrier V S V G V T V D Source Drain reservoirs
The MOSFET transistor : operating principle V(0) = VGS VT I Liquid flow dv ( x) = α WV( x) dx VGS V(x) V DS volume slope speed Source 0 x V T L G Drain V( L ) = V V V G GS T DS Steady-state regime αw 2 2 I = V (0) V ( LG ) L G After simplification 2 αw V DS I = ( VGS VT ) VDS L G 2
The MOSFET transistor : operating principle Saturation as soon as V < V V < 0 DS GS T V GS 0 x V(x) V T V DS Source L G Saturation current αw I = ( V ) 2 GS VT 2L G Drain With a bit more of theory α = µ C p ox µ p : hole mobility C ox : capacitance per unit area
The MOSFET transistor : operating principle Ohmic region I D V SDsat I = K ( VGS VT ) VDS V 2 2 DS saturation zone V<V<0 GS T Current source region K I = ( VGS VT ) 2 2 V SD V>V GS T with : = µ W K Cox L G
The MOSFET transistor : operating principle What it is necessary to retain 1 I L G If L G decreases, the current flowing in the transistor increases
The numerical integrated circuit star The CMOS logic gates
A basic logic-gate : the CMOS inverter In digital electronics, the transistor is used as a switch G NMOS D G PMOS D S S OFF 0 V TN ON V GS ON V TP 0 OFF V GS
A basic logic-gate : the CMOS inverter V DD G PMOS S D I ON ON V TP OFF 0 V GS P V E NMOS S C V S OFF 0 V TN ON V GS N V GS N =V E V GS P =V E -V DD
A basic logic-gate : the CMOS inverter V DD G PMOS S D I ON ON OFF V E V E NMOS S C V S 0 OFF V TN ON V DD +V TP V DD
A basic logic-gate : the CMOS inverter V DD V E =0 case PMOS ON OFF I ON V E NMOS C V S 0 OFF V TN ON V DD +V TP V DD V E =0 V S =V DD
A basic logic-gate : the CMOS inverter V DD V E =V DD case PMOS ON OFF I ON V E NMOS C V S 0 OFF V TN ON V DD +V TP V DD V S =0 V E =V DD
A basic logic-gate : the CMOS inverter The circuit speed is linked to the charge/discharge of the capacitor C To increase the frequency of the circuits, we need to increase the current flowing in the transistors The length of the gate is worth to be decreasing
Lecture plan Towards the nanotechnologies... data storage The data processing through the ages MOS transistor in logic-gates gates The microelectronics of today : MOSFET s chronicle of a death foretold? The possible alternatives Coulomb blockade for the nanoelectronics
The microelectronics of today MOSFET s chronicle of a death foretold?
MOSFET transistor : chronicle of a death foretold? The roadmap... Gate length (µm) 10 1 0.1 256ko 1,6µm 1Mo 4Mo 16Mo Bell Labs 0,14µm 64Mo 256Mo 0,15 µm 512Mo 1Go2Go IBM 0,1µm 6Go Toshiba 40nm 16Go 48Go 30nm LETI 20nm ST 16nm 0.01 1980 1985 1990 1995 2000 2005 2010 2015 2020 Production Estimation Research
MOSFET transistor : chronicle of a death foretold? 1947 1958 1971 Today 2001 2002 Today Pentium IV 0.13 µm 50.000.000 Tr. f=3 GHz P~100 W
Integrated circuit scale Department 75 75 km 2 Integrated circuit 2 2 cm 2 Headlight of truck 30 cm France 550.000 km 2 Truck 2,5 m 10 m CMOS inverter 1,5 µm 1,5 µm (Lay out) Wafer 700 cm 2 Transistor gate < 0,1 µm
MOSFET transistor : chronicle of a death foretold? 1947 1958 1971 Today 2001 2002 Research STMicroelectronics 16 nm 2001
MOSFET transistor : chronicle of a death foretold? 1947 1958 1971 Today 2001 2002 Research Intel 15 nm 2002
MOSFET transistor : chronicle of a death foretold? oxide thickness thiner and thiner V DD (voltage breakdown) leakage tunnel currents appear P static t retention e ox Source Drain ZCE V DS L G Solution: e ox to improve gate control Substrat Proximity source-drain I OFF g m Quantization phenomena e max e min relative error of SiO 2 layer thickness device parameter dispersion
Lecture plan Towards the nanotechnologies... data storage The data processing through the ages MOS transistor in logic-gates gates The microelectronics of today : MOSFET s chronicle of a death foretold? The possible alternatives Coulomb blockade for the nanoelectronics
The possible alternatives or how the nanotechnologies can save the electronics...
The carbon nanotubes
The magnetic nanocolumns Today Contribution of nanotechnologies granulary film in-plane magnetization 100 grains/bit nanometric columns perpendicular magnetization 1 bit per column
Molecular electronics A memory example Difficulty of realization J. SÉE - VSOP 2004-2005 Lecture on Coulomb blockade for nanoelectronics