Leakage current of device HEMT versus MOSFET

2005-21482이진식

MDCL Jin Sik Lee

Outline

Introduction

HEMT

MOSFET

conclusion

MDCL Jin Sik Lee

introduction

Nowadays leakage power dissipation is a big issue

According to aggressive scaling of CMOS with higher integration density

Scaled device results in the drastic increase of total leakage power

It degrades the performance of device We must minimize the leakage current

MDCL Jin Sik Lee

HEMT

Leakage current Gate leakage current Off state IDSleakage current

MDCL Jin Sik Lee

Gate leakage current

C has very high leakage current Leakage current affect the power gain and noise

performance With a short distance, heavy doping, high leakage

current is occurred Wide band-gap semiconductor under the gate must be

of highest quality to form low leakage current

MDCL Jin Sik Lee

AlGaN-GaN:surface defect

RF and power electronics High carrier mobility High breakdown voltage

Schottky gate leakage In reality10-5 order, it ideally must

be 1uA/mm The influence of the surface charge

upon the gate leakage current is modeled

Process damage such as nitrogan vacancy

Inducing large tunneling current

Fig 1.electric field concentration at the edge

Fig 2.schottky barrier thinning

Fixed positive charge

MDCL Jin Sik Lee

AlGaN-GaN:surface defect positive defect

charge increases the electric field

With the increase of defect charge

leakage current increase Low breakdown voltage

Field plate electrode structure

Uniformly distributed field

Fig 4.AlGan-GaN HEMT with surface damaged

Fig 5.Sumulated off-state curve

MDCL Jin Sik Lee

FP devices have lower gate leakage current compared to the no-FP device

The influence of the defect charge decreases with the increase of FP length

AlGaN-GaN:surface defect

MDCL Jin Sik Lee

AlGaN-GaN:copper gate

Copper gate AlGaN/GaN with low gate leakage Schottky barrier height of Cu on n-GaN is 0.18eV higher than NiAu Gate resistance of copper is 60% as that of NiAu Low leakage, low resistivity, good adhesion for gate metal for power devi

ce. Resistivity:1.7uΏ/cm,

I-V characturistics of a Cu

and a Ni/Au Schottky contact gate leakage current under drain 0.1V and 10v

for a Cu gate and a Ni/Au gate

MDCL Jin Sik Lee

Low standby leakage current

E-mode junction pseudomorphic HEMT with a high Vt

h

High turn-on voltage VF(1.3V)at 1mA/mm

Single power supply PA When the Vth is near VF,gat

e current increases. Key Point:high VF(1.3v)

Enhancement-mode JPHEMT with a high VF

IGS-VGS characteristic of the conventional

and the novel JPHET

MDCL Jin Sik Lee

MOSFET

Subthreshold leakage current

Gate leakage current

R-biased band-to-band leakage current

Figure 1.Major leakage components

MDCL Jin Sik Lee

MOSFET

Relative leakage components becomes equally important

For 90-nm, the major leakage components is the subthreshold.

In the scaled device, contribution of junction and gate leakage have significantly increased

MDCL Jin Sik Lee

Subthreshold leakage current

SS=2.3*kt/q(1+Cdm/Cox) Slight dependent on cons

Independent of Vds The effect of trap density Halo doping method Practically it is a function of te

mperature dVt/dT~-1mV/k

Log(

Ids)

sca

le

Lin

ear Id

s

scale

Vth Vg

Ids

MDCL Jin Sik Lee

Halo(pocket) implant doping method is choosed to improve not only subthreshold leakage current but also short channel effect or something

Localized implant doping is done near source/drain

The higher doping reduces the source/drain. depletion widths and prevents their interaction such as charge sharing, DIBL

disadvantge:BTBT leakage current

Subthreshold leakage current

N+N+

p-sub

P+ P+

gate

HALO

MDCL Jin Sik Lee

Gate leakage current

As gate length becomes more smaller, thin oxide thickness is also needed

Short channel effect There is a constraint to meet the requirements that people wa

nt As tox becomes thin, tunneling leakage current may hap

pen High k material such as HfO2is studied broadly Impact ionization

MDCL Jin Sik Lee

conclusion

Leakage current is a big issue It degrades the performance of device It dissipates unnecessary power

HEMT Surface defect, Gate material

MOS Subthreshold, gate, BTBT

It is important to minmize the leakage current considering other points

MDCL Jin Sik Lee

Reference

Subthreshold leakage modeling and reduction techniques [IC CAD tools]Kao, J.; Narendra, S.; Chandrakasan, A.;Computer Aided Design, 2002. ICCAD 2002. IEEE/ACM International Conference on10-14 Nov. 2002 Page(s):141 - 148

Accurate estimation of total leakage in nanometer-scale bulk CMOS circuits based on device geometry and doping profileMukhopadhyay, S.; Raychowdhury, A.; Roy, K.;Computer-Aided Design of Integrated Circuits and Systems, IEEE Transactions onVolume 24, Issue 3, March 2005 Page(s):363 - 381

Modeling subthreshold leakage and thermal stability in a production life test environmentBlack, K.; Kelly, K.; Wright, N.;Semiconductor Thermal Measurement and Management Symposium, 2005 IEEE Twenty First Annual IEEE15-17 March 2005 Page(s):223 - 228

Off-state breakdown effects on gate leakage current in power pseudomorphic AlGaAs/InGaAs HEMTsChou, Y.C.; Li, G.P.; Chen, Y.C.; Wu, C.S.; Yu, K.K.; Midford, T.A.;Electron Device Letters, IEEEVolume 17, Issue 10, Oct. 1996 Page(s):479 - 481