1. L. Head//ECE Dept./Rowan University Engineering Electromagnetics 1 0909.301.01 Fall 2004 Linda Head ECE Department Rowan University http://engineering.rowan.edu/~shreek/fall04/eemag1/lectures/mosfets.ppt INTRODUCTION TO MOSFETS October 6, 2004

2. L. Head//ECE Dept./Rowan University Silicon - Four Cases Si Intrinsic Si - 0 o K P-type Si N-type Si Si h+ e - Intrinsic Si - Room Temp Si B- h+ e - h+ Si + e - Ph h+ e -

3. L. Head//ECE Dept./Rowan University Metal-Oxide-Semiconductor Capacitor Metal SiO 2 n+ polysilicon p-type silicon

4. L. Head//ECE Dept./Rowan University Looks Like……. Insulator Conductor

5. L. Head//ECE Dept./Rowan University The positive charge on the metal is matched by negative charge from the ions in the p-type semiconductor. The h+ just get pushed away from the interface between the insulator and the p-type semiconductor leaving only the “stuck” charged atoms. We call this the depletion region - we now have a 2-layer insulator. +V SiO 2 Metal and Polysilicon p-type Si Gnd.

6. L. Head//ECE Dept./Rowan University Once a maximum width is reached for the “depletion region” the electrons in the material are attracted to the SiO2 / p-type Si interface and now there is an channel of electrons right underneath the SiO2 ++V SiO 2 Metal and Polysilicon p-type Si Gnd. Electron Channel

7. L. Head//ECE Dept./Rowan University MOSFET Operating Regions

8. L. Head//ECE Dept./Rowan University Depletion Region Al n + Polysilicon Si 0.4 V 0 V

9. L. Head//ECE Dept./Rowan University Inversion Region 1.0 V 0 V

10. L. Head//ECE Dept./Rowan University Linear Region 0.25 V 1 V

11. L. Head//ECE Dept./Rowan University Pinch-Off Region 1 V 1.5 V

12. L. Head//ECE Dept./Rowan University Things You Need To Know  r(Si) = 11.8  r(SiO2) = 3.9 The length of the “channel” is 1. The n+ source and drain, the polysilicon and the p+ semiconductor are metal-like conductors.