2009 VLSI (NCTU, S.Chung, eSiGe on extension)

2009 VLSI (NCTU, S.Chung, eSiGe on extension)

Chung, S.S.; Hsieh, E.R.; Liu, P.W.; Chiang, W.T.; Tsai, S.H.; Tsai, T.L.; Huang, R.M.; Tsai, C.H.; Teng, W.Y.; Li, C.I.; Kuo, T.F.; Wang, Y.R.; Yang, C.L.; Tsai, C.T.; Ma, G.H.; Chien, S.C.; Sun, S.W., “Design of high-performance and highly reliable nMOSFETs with embedded Si:C S/D extension stressor(Si:C S/D-E),” VLSI Technology, 2009 Symposium on , vol., no., pp.158-159, 16-18 June 2009

Abstract: A Novel strained nMOSFET with embedded Si:C in S/D extension stressor (Si:C S/D-E) was presented. Comparing to the bulk device, it revealed good drive current ION (+27%), high ID,sat current (+67%), enhanced channel mobility (+105%), at a lower effective substitutional carbon concentration (C%=1.1%), using the poly-gate 40 nm-node Si:C/eSiGe S/D CMOS technology. Moreover, PBTI effect was first observed in this device as a result of carbon impurity out-diffusion, which is of critically important for the design trade-off between performance and reliability.

URL: http://ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=5200671&isnumber=5200578

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Table 1 The comparison of this work with published data for nMOSFETs with Si:C S/D stressor

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Since C implantation and SPE
can be integrated in the S/D region after the spacer or into
extension S/D before the spacer, Si:C S/D, 3(a) and Si:C
S/D-E, (3b), respectively, both were used to study the strain
effect. The control was also made for comparison.
Figs. 4(a) and 4(b) show the simulated profiles of
longitudinal stress (Sxx) for the Si:C S/D and Si:C S/D-E
devices, respectively. It can be found from Sxx that the Si:C
S/D-E device introduces more strain into the channel, and the
C% of Si:C S/D-E devices is higher thanks to a lower dopant
interference in the area below the extension S/D junction.
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Fig. 5, the Ion-Ioff curve of the Si:C S/D-E devices shows 27%
current gain over the control (bulk-Si) and 14% improvement
for typical Si:C S/D devices.

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As shown in Fig. 7, the peak mobility of the Si:C
S/D-E devices exhibits a 105% increase in comparison to the
control. Furthermore, Fig. 8 shows that Ron of the Si:C S/D-E
devices has been reduced 26%.

The Si:C S/D-E device shows a larger
degradation comparing to the control. As a trade-off, we may
reduce the C%-dose to improve the reliability.
Fig. 13 shows
the ID-VDS curves of the Si:C S/D-E devices with typical and
low C%-dose and the control, and the device with low dose
still maintains an enhancement of 50% over the control

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ID degradations of these three devices are evaluated in Figs.
14(a), in which the device with low dose shows a largely
reduced ID degradation and is comparable to the control. Also,
the PBTI effect was improved in Fig. 14(b), in which we
conclude that a larger C%-dose in the channel will give rise
to a much worse degradation. This is believed to be caused
by the carbon out-diffusion during PBTI stress.

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