Channel Length Dependence of Negative Bias Temperature Instability on pMOSFETs with either B- or BF[sub 2]-Implanted Source/Drain

Abstract

We evaluated the channel length dependence of the negative bias temperature instability in deep-submicrometer p-type metal oxide semiconductor field effect transistors (pMOSFETs) having either a boron- or BnormalF2 -implanted source/drain (S/D) and a poly-Si film. We found that long-channel-length (10μm) pMOSFETs having a BnormalF2 -implanted S/D exhibit a larger negative threshold voltage shift (ΔVth) than do those having a B-implanted S/D. This phenomenon indicates that fluorine atoms enhance boron diffusion into the gate oxide region, resulting in the increase in fixed-positive oxide charges and the decreased density of interface states. In contrast, the shorter-channel-length device having a BnormalF2 -implanted S/D displays a smaller value of ΔVth than does that possessing a B-implanted S/D. These observations indicate that fluorine atoms not only induce negative interface states but also suppress the positive interface traps that occur during NBTI stressing.

Investigating the NBTI effect on P- and N-substrate MOS capacitors and p-MOSFET transistors

“…We note that ILl V, hl decreases when the channel length increases. This result is in good agreement with several works reported in literature [4][5][6]. This gate length dependence suggests that the NBT!…”

“…It has been reported that the effective channel length effect on NBTI degradation has an important role [4][5][6][7][8]. It is generally observed that threshold voltage shift (LI V,h) caused by NBTI stress is enhanced by reduction of the channel length [4][5][6], indicating a spatially nonuniform degradation along the channel.…”

“…It is generally observed that threshold voltage shift (LI V,h) caused by NBTI stress is enhanced by reduction of the channel length [4][5][6], indicating a spatially nonuniform degradation along the channel. It has been suggested that the charge of defect density near the gate edge, including the gate source/drain overlapping regions, is higher than that in the middle region of channel.…”

Characterization and modeling of negative bias temperature instability in P-MOSFETs

“…2.10, the reduction of NBTI increases as the implanted fluorine dose increases. This fluorine-improved NBTI phenomenon was observed and further confirmed by many other researchers [35,97,[101][102][103]. The improvement of NBTI by fluorine is mainly attributed to the formation of stronger Si-F bonds at the interface, which increases the resistance against NBTI degradation.…”

“…It is believed that boron can diffuse into the gate oxide from the boron-doped gate. Figure 2.9(b) shows that boron penetration could suppress the NBTI-induced interface trap generation, which was mainly attributed to the formation of Si-F bonds from the BF 2 -based boron implantation [97]. However, as can be seen in Fig.…”