1. Lecture 12 Power Devices (2)
Si Power MOSFET
VMOSFET
UMOSFET
DMOSFET
LDMOSFET
V=Vertical

2. DMOSFET
D: Diffused

3. UMOSFET
U=U-groove

4. Forward blocking capability
- Gate is short to source; no surface channel
p-base-n-drift-layer junction become revers-biased and supports the positive drain voltage
The peak p-base doping controls VT. Typical 2-3 V. nAP=1E17/cm3

5. Threshold voltage (2-3V)
Ideal Model:
More realistic model:

6. Channel Resistance
Pinch off at VD=VG-VT >>>>> Saturation

7. Specific on-resistance (DMOSFET)
The ideal Ron,sp for 50 V could be 0.1 mΩ-cm2

8. Si LDMOSFET For wireless base-station RF power amplifier a few GHz
W power output
Motorala is the primary supplier

9. Rscont Rp-ch-cont Rdcont RLDD Rch Rshunt Rp+-sub SiO2 n+ p-channel n
p- epi
p+ sub
p-channel
SiO2 n 1u

10. Equivalent Circuit of RF LDMOSFETRd
Cgd Rg
GmVgs
Cds
Vout
Cgs
Vin Rs
Feature
Low Rg(thicker TiSi2), Rshunt(enhanced p-channel), Rs(heavier n+ source & thinner substrate)
Low Cgs in ARF4 (0.6u); Low Cgd due to less gate/LDD area & shallow LDD junction; Low Cds due to buffered drain
Reduced Hot-carrier effect due to lower E-field in channel, improved gate oxide, and buffered drain

11. Layout of Single Metal Approach (Approach1-2)
1,330um
5,400um

12. Approach 3-4: 2-layer metal with gate strapping L60u &L100u
1,330um
5,400um

13. Package of AGR19090 LDMOS Package Output Capacitor Integrated Standoff
LDMOS Die
Input Capacitor

14. Handle approach devices Si (200 m) Polyimid Si (7-50 m) Cu heat sink
Solder
Layouts:
50u gate finger structure
50u gate finger structure with V-groove outside the active area
3x100u gate finger with metal stack and rotated gate strips(Mot.)
5x100u with our approach

15. Simulation of Dummy Gated LDMOS
Equal-potential line contours of conventional LDMOS (ARF3, ARF4, Motorola)
Equal-potential line contours of dummy gated LDMOS

16. Simulation of Dummy Gated LDMOS
Electric field contours of conventional LDMOS (ARF3, ARF4, Motorola)
Electric field contours of dummy gated LDMOS

17. Electric field distribution along the surface of LDMOS, and DG-LDMOS
Channel
LDD
LDMOS
DG-LDMOS
Electric field distribution along the surface of LDMOS, and DG-LDMOS

18. MRF284 DCIV pre/post HCI

19. Homework: Read and study Chapter 4 Power Device pp
Homework: Read and study Chapter 4 Power Device pp “Modern Semiconductor Device Physics”