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2009 SEMICONDUCTORS AND NANOSTRUCTURESMagnetoresistance mobility extraction in FinFET triple gate devicesWe have applied the geometric magnetoresistance (MR)technique to FinFET devices. The geometric µ MR mobilityis give by ρ(B) = ρ 0 (1 + µ 2 MR B2 ) where ρ 0 is the zeromagnetic field (B = 0) resistivity. The devices studied inthis work are triple-gate FinFET from IMEC in Belgium.The devices characteristics used are: oxide thickness of2 nm (EOT), fin height of 60 nm, channel width (W f in )of 10µm, the channel length (L) varies from 90 − 910 nm.The electrical characteristics were acquired using a semiconductorparameter analyzer (HP 4156A) measuring thedrain current-voltage I D (V G ) curves at different magneticfields, low temperatures and for low drain bias (linear region:V DS = 50 mV) in order to compute the µ MR . Thismethod works for transistor length much smaller than thewidth (typically W/L > 5).Another problem with the use of short devices at low temperaturesis the series resistance effect. Figure66(b) showsthat there is a reduction of the mobility with decreasingchannel length, while for long channels, the phonon scatteringis dominant. However, it is noted that the mobility increasesis attenuated for shorter devices, owing to the largeseries resistance, which masks the mobility enhancement atlow temperature.In order to obtain the µ MR , we plot the µ MR resistance ratioR(B)/R 0 for various values of V G as a function of B 2as shown in figure 65 for typical transistor with a channellength of 410 nm, fin width of 10µ m at T = 100 K. Theother devices measured present the same behaviour.From the slope of this curve, for each applied gate voltageV G , the mobility µ MR can be calculated. The mobility µ MR isplotted as a function of V G in figure 66(a). In order to makea comparison, we also plott the variations of effective mobilityµ e f f and field-effect mobility µ FE . These curves havebeen calculated by taking µ FE = gm/((W/L)C ox V D ) andµ e f f = √ µ 0 − µ FE at B = 0. The low electric-field mobilityµ 0 were extracted using Y (V G ) = I D / √ gm(V G ), whichallows us to eliminate the first-order mobility attenuationfactor and source-drain series resistance effects [Ghibaudo,Electron Lett. 24, 543 (1988)]. While here we present resultsfor one transistor at one temperature, for all the transistorsmeasured, at three different temperatures (77K, 100Kand 200K), same behaviour was observed.Figure 65: µ MR ratio R(B)/R 0 in function of square of magneticfield for different values of gate bias. The symbol line representsthe “intrinsic” mobility ratio µ 0 (0)/µ 0 (B) extracted from the Y–function. For L = 410 nm and T = 100 K.In figure 65 we plot the low-field mobility ratioµ 0 (0)/µ 0 (B) as a function of B 2 that was extracted by thestandard relation µ 0 (B) = µ 0 /(1+µ 2 0,MR B2 ). From the slopeof these lines it is possible to extract the low-field MR mobilityµ 0,MR (figure 66 (b) that is independent of both thegate bias and the magnetic field.Figure 66(b) shows the µ 0,MR and µ 0 for transistors as afunction of the channel length, for different temperatures.µ 0,MR is higher than µ 0 for all temperatures. As the temperaturedecreases there is an increase in the mobility dueto the reduced phonon scattering [Ohata, ESSDERC 2004,109 (2004)].Figure 66: a)Variations of µ MR mobility, effective mobility andfield effect mobility (corresponding to a zero magnetic field) versusgate voltage. For L = 410 nm and T = 100 K. b) Low-field mobilityµ 0 and low-field, MR mobility µ 0,MR versus channel lengthat different temperaturesD.K. MaudeC. D. G. dos Santos , J. A. Martino (EPUSP- Escola Politécnica da Universidade de São Paulo, São Paulo, Brazil), S.Cristoloveanu (IMEP, Grenoble, France)49