CMOS Technology Flow varies with process types & company N-Well CMOS Twin-Well CMOS STI Start with substrate selection Type: n or p Doping level, →resistivity Orientation, 100, or 101, etc Other parameters
N-well CMOS (ON.5um) pMOS transistors in n-well nMOS transistors on substrate nMOS transistor’s body is always connected to lowest voltage of chip nMOS is a three terminal device pMOS body can be tied to voltages other than Vdd pMOS is a four terminal device 0.35um and larger typically n-well
VDD M2 Vin Vo M1
Relative size of different layers
Deep SubMicron Challenges Transistor sizes become very small But FOX lateral size cannot be reduced Depletion region between p-well and n-well not reduced Large area FOX depletion
Shallow Trench Isolation Technology Allowing transistors to be spaced closer
Devices available Transistors and wires Deep wells good for substrate noise isolation
Resistors Diffused and/or implanted resistors. Well resistors. Polysilicon resistors. Metal resistors. Thin film resistors
capacitors In older processes, you put the bottom plate on FOX Junction capacitors Gate capacitors Poly-poly capacitors Metal-metal capacitors In older processes, you put the bottom plate on FOX
Metal-metal capacitors Very linear cap More expensive to make
Inductors
Sub 100nm CMOS Technology State of the art is 14 nm 45 nm is in wide use for high speed 65 nm also in wide use for SoCs Grad students in our group have access to certain 28nm, 45 nm, 65 nm, 130nm, 180nm, 0.5mm technologies Have designed in such technologies But analog transistors use L = 0.6, 0.9 mm
HW Go to the MOSIS webpage Find and download the NDA for IBM0.13 Sign it, either give to TA in person, or scan and email to TA
Advantages Digital Viewpoint: Analog Viewpoint: Improved Ion/Ioff Reduced gate capacitance Higher drive current capability Reduced interconnect density Reduction of active power Analog Viewpoint: More levels of metal Higher fT Higher capacitance density Reduced junction capacitance per gm
Disadvantages for analog Reduction in power supply resulting in reduced headroom and signal power Gate leakage currents Reduced small-signal intrinsic gains Increased nonlinearity (IIP3) Noise and matching?? Reduced signal to noise ratio Anne-Johan Annema, et. Al., “Analog Circuits in Ultra-Deep-Submicron CMOS,” IEEE J. of Solid-State Circuits, Vol. 40, No. 1, Jan. 2005, pp. 132-143.
the Gate Leakage Problem