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Predictive and Efficient Modeling of Hot Carrier Degradation with Drift-Diffusion Based Carrier Transport Models

8.3 EES Affecting the Temperature Behavior of HCD

The effect of EES also plays an important role in determining the temperature behavior of

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Figure 8.16: DFs near the drain region of a 44 \( \, \)nm SiON nMOSFET at \( V_{\mathrm {gs}} \) = \( V\mathrm {_{ds}} \) = 2 \( \, \)V simulated with ViennaSHE for two temperatues, 25 \( \, \)oC and 75 \( \, \)oC. The hump in the DFs caused by EES is visible in the high energy region [88].

HCD in short channel devices. In [88], SiON nMOSFETs with an effective channel length of 44 \( \, \)nm were subjected to hot-carrier stress under Vds = Vgs = 1.8, 2.0, and 2.2 V and at two different temperatures, i.e. T = 25 and 75 \( \, \)oC. To asses HCD, \( I_{\mathrm {d,lin}}(t) \) traces were recorded up to \( \sim \)9 ks. For \( V_{\mathrm {ds}} \) = \( V_{\mathrm {gs}} \) = 1.8 and 2.0 \( \, \)V, \( I_{\mathrm {d,lin}} \) values for T = 25 \( \, \)oC are higher than those for T = 75 \( \, \)oC. This result contradicts previous findings obtained in transistors with comparable gate lengths (e.g. [5] and [6]). Also, the distance between \( I_{\mathrm {d,lin}}(t) \) curves reduces as \( V_{\mathrm {ds}} \), \( V_{\mathrm {gs}} \) increase, and at \( V_{\mathrm {ds}} \) = \( V_{\mathrm {gs}} \) = 2.2 \( \, \)V the \( I_{\mathrm {d,lin}} \) values are almost the same for both temperatures within the whole stress time slot. This is because the rate of the MC-process was found to decrease with increase in temperature while the rate of the SC-process, augmented by EES, increases with temperature. Thus, as shown in Figure 8.16, the DFs have higher values at 25 \( \, \)oC in the lower energy region dominated by MC-mechanism. While higher DF values are observed at 75 \( \, \)oC for the energy tails including the EES hump where the SC-mechanism of bond dissociation dominates. This trend is also evident from the distance between the \( I_{\mathrm {d,lin}}(t) \) curves obtained for the two temperatures increasing when the SC-process is neglected.