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Integrated Circuit Devices

Integrated Circuit Devices. Professor Ali Javey Summer 2009. MOSFETs Reading: Chapters 17 & 18. The First Transistor. 1956 Physics Nobel Prize. Invention of the Field-Effect Transistor. In 1935, a British patent was issued to Oskar Heil. A working MOSFET was not demonstrated until 1955.

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Integrated Circuit Devices

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  1. Integrated Circuit Devices Professor Ali Javey Summer 2009 MOSFETs Reading: Chapters 17 & 18

  2. The First Transistor

  3. 1956 Physics Nobel Prize

  4. Invention of the Field-Effect Transistor In 1935, a British patent was issued to Oskar Heil. A working MOSFET was not demonstrated until 1955.

  5. Today’s MOSFET Technology Gate oxides as thin as 1.2 nm can be manufactured reproducibly. Large tunneling current through the oxide limits oxide-thickness reduction.

  6. Introduction to the MOSFET Basic MOSFET structure and IV characteristics

  7. Introduction to the MOSFET Two ways of representing a MOSFET:

  8. Complementary MOSFETs (CMOS) NFET PFET When Vg = Vdd , the NFET is on and the PFET is off. When Vg = 0, the PFET is on and the NFET is off.

  9. Qualitative discussion: n-MOSFET VG > VT ; VDS 0 ID increases with VDS VG > VT; VDS small, > 0 ID increases with VDS , but rate of increase decreases. VG > VT; VDS pinch-off ID reaches a saturation value, ID,sat The VDS value is called VDS,sat VG > VT; VDS > VDS,sat ID does not increase further, saturation region.

  10. Threshold voltage for NMOS and PMOS When VG = VT, s = 2 F; we get expression for VT. Ideal n-channel (p-silicon) device both terms positive Ideal p-channel (n-silicon) device both terms negative Si / ox = = 11.9 / 3.9  3 F > 0 means p-type F < 0 means n-type

  11. I ds V = 10mV ds V gs V t How to Measure the VT of a MOSFET Vt is measured by extrapolating the Ids versus Vgs (at low Vds) curve to Ids = 0.

  12. Quantitative ID-VDS Relationships “Square Law” ; ID will increase as VDS is increased, but when VG – VDS = VT, pinch-off occurs, and current saturates when VDS is increased further. This value of VDS is called VDS,sat. i.e., VDS,sat = VG – VT and the current when VDS= VDS,sat is called IDS,sat. ; Here, Cox is the oxide capacitance per unit area, Cox = ox / xox

  13. ID-VDS characteristics expected from a long channel (L << L) MOSFET (n-channel), for various values of VG

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