1. Reading: Finish Chapter 19.2
Lecture #43
OUTLINE
Short-channel MOSFET (reprise)
SOI technology
Reading: Finish Chapter 19.2
EE130 Lecture 43, Slide 1

2. OUTPUT CHARACTERISTICS TRANSFER CHARACTERISTICS
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

3. Silicon on Insulator (SOI) Technology
TSOI
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
EE130 Lecture 43, Slide 3

4. Partially Depleted SOI (PD-SOI)
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 ID vs. VDS curve
EE130 Lecture 43, Slide 4

5. Fully Depleted SOI (FD-SOI)
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
Silicon Substrate
Source
Drain
SiO2
SOI
Gate
EE130 Lecture 43, Slide 5