Leakage current of device HEMT versus MOSFET 이진식

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 I DS leakage 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 device. 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 V th High turn-on voltage VF(1.3V)at 1mA/mm Single power supply PA When the V th is near V F,gate current increases. Key Point:high V F(1.3v) Enhancement-mode JPHEMT with a high V F 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 temperature dVt/dT~-1mV/k Log(Ids) scale Linear Ids scale VthVg 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+ p-sub 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 want As t ox becomes thin, tunneling leakage current may happen High k material such as HfO 2 is 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, ICCAD IEEE/ACM International Conference on Nov Page(s): Accurate estimation of total leakage in nanometer-scale bulk CMOS circuits based on device geometry and doping profile Mukhopadhyay, S.; Raychowdhury, A.; Roy, K.; Computer-Aided Design of Integrated Circuits and Systems, IEEE Transactions on Volume 24, Issue 3, March 2005 Page(s): Modeling subthreshold leakage and thermal stability in a production life test environment Black, K.; Kelly, K.; Wright, N.; Semiconductor Thermal Measurement and Management Symposium, 2005 IEEE Twenty First Annual IEEE March 2005 Page(s): Off-state breakdown effects on gate leakage current in power pseudomorphic AlGaAs/InGaAs HEMTs Chou, Y.C.; Li, G.P.; Chen, Y.C.; Wu, C.S.; Yu, K.K.; Midford, T.A.; Electron Device Letters, IEEE Volume 17, Issue 10, Oct Page(s):