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Kijeong Han

khan5@ncsu.edu

A 1200 V 4H-SiC Planar MOSFET Optimization

for High Frequency Figure-of-merit Principal Investigator: Dr. Jayant Baliga

North Carolina State University (NCSU)

v  Objective

v  Structure Optimization

¨ 4H-SiC Power MOSFET with improved high frequency Figure-of-merit

- Figure-of-merit (FOM) : R x C, R x Q

- Structure optimization : R ↓ è Conduction loss ↓ C, Q ↓ è Switching loss ↓

Gate

                                                                                               JFET      

N-­‐  DriR

   

P+  body N+  source

N+  sub Drain

Gate Source

LA  

BP1 structure

Objec?ve

① JFET width ↓ + doping ↑ ② Channel length ↓ ③ P+ body contact

¨ Cell pitch ↓

Gate

                                                                   

N-­‐  DriR

           

P+  body  

N+  source

N+  sub Drain

Gate  S

BP2 structure

   

JFET  LA   P+ body contact

Orthogonal to cross section

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FOM ↓

v  Simulation Results Wcell [µm]

BV [V]

CGD,sp [nF/cm2]

QGD,sp [nC/cm2]

Ron,sp [mΩ ⋅ cm2]

FOM (= CGD x Ron) [mΩ ⋅ nF]

BP1 11 1392 0.168 355 6.75 1.134

BP1  Characteris?cs

[ Qg simulation ↑ ] [ BV simulation → ]

[ ↓ IV simulation ]

@freq. : 100 kHz

7.54  pF  

@area : 4.5 mm2

7.68  pF  [ ← CGD simulation

& CGD measurement ]

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v  Simulation Results

§  LA : 1.7 µm (BP1) §  LA : 0.7 µm

< E-field (BV = 1392 V) > < E-field (BV = 1620 V) >

@Limit of Oxide Field : 4 MV/cm

@JFET doping : 8x1015 cm-3

JFET  Op?miza?on  (1/2)

< Current flow (Ron,sp = 6.75 mΩ⋅cm2) > < Current flow (Ron,sp = 10.84 mΩ⋅cm2) > 35  

   

   

: FOM

@freq. : 100 kHz

: Cgd,sp

: Ron,sp

JFET doping (cm-3)

LA (µm)

BV (V)

Ron,sp (mΩ-cm2)

Cgd,sp (pF/cm2)

FOM (Ron,sp x Cgd,sp) (mΩ-pF)

~4e16

0.7 1614 4.55 81.46 370.6 (x 3) 1 1526 4.04 113.92 460.2

1.5 1192 4.06 155.84 632.7 2 988 4.17 208.9 871.1

2.5 875 4.31 254.29 1096.0 3 808 4.43 293.72 1301.2

@VDrain : 1000 V

: BV

JFET  Op?miza?on  (2/2)

Cgd,sp  simulation

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v  Summary of Characteristics

Wcell [µm]

BV [V]

CGD,sp [nF/cm2]

QGD,sp [nC/cm2]

Ron,sp [mΩ⋅cm2]

FOM (= CGD x Ron)

[mΩ ⋅ nF]

FOM (= QGD x Ron)

[mΩ ⋅ nC]

BP1 11 1392 0.168 355 6.75 1.134 2398

BP2 5.6 1613 0.0928 233 3.47 0.322 (x3.52) 808.86 (x2.96)

Figure-­‐Of-­‐Merit  (FOM)

BP1 structure

① JFET width ↓ + doping ↑

② Channel length ↓

③ P+ body contact

BP2 structure

§  NJFET : 0.8e16 cm-3 §  LA : 1.7 µm §  LCH : 0.8 µm §  Wcell : 11 µm

§  NJFET : ~4e16 cm-3 §  LA : 0.7 µm §  LCH : 0.5 µm §  Wcell : 5.6 µm

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