60 likes | 324 Views
OUTLINE Short-channel MOSFET (reprise) SOI technology Reading: Finish Chapter 19.2. Lecture #43. Short-Channel MOSFET. OUTPUT CHARACTERISTICS. TRANSFER CHARACTERISTICS. I DS does not saturate with increasing V DS due to DIBL, and also channel-length modulation for V DS > V GS - V T.
E N D
OUTLINE Short-channel MOSFET (reprise) SOI technology Reading: Finish Chapter 19.2 Lecture #43 EE130 Lecture 43, Slide 1
Short-Channel MOSFET OUTPUT CHARACTERISTICS TRANSFER CHARACTERISTICS • IDS does not saturate with increasing VDS due to DIBL, and also channel-length modulation for VDS>VGS-VT EE130 Lecture 43, Slide 2
Transistors are fabricated in a thin single-crystal Si layer on top of an electrically insulating layer of SiO2 Simpler device isolation savings in circuit layout area Low junction capacitances faster circuit operation Better soft-error immunity No body effect Higher cost Silicon on Insulator (SOI) Technology TSOI EE130 Lecture 43, Slide 3
Floating body effect (history dependent): When a PD-SOI NMOSFET is in the ON state, at moderate-to-high VDS, holes are generated via impact ionization near the drain Holes are swept into the neutral body, collecting at the source junction The body-source pn junction is forward biased VT is lowered IDsat increases “kink” in output IDvs.VDS curve Partially Depleted SOI (PD-SOI) EE130 Lecture 43, Slide 4
No floating body effect! VT is sensitive to SOI film thickness Poorer control of short-channel effects due to fringing electric field from drain Elevated S/D contact structure needed to reduce RS, RD Gate Source SOI Drain SiO2 Silicon Substrate Fully Depleted SOI (FD-SOI) EE130 Lecture 43, Slide 5