Archive for the ‘ Process induced strain ’ Category

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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The
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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eSiC for NMOS

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

2009 VLSI TSA
Liu, P.W.; Kuo, T.F.; Li, C.I.; Wang, Y.R.; Huang, R.M.; Tsai, C.H.; Tsai, C.T.; Ma, G.H., “Dopant and thermal interaction on SPE formed SiC for NMOS performance enhancement,” VLSI Technology, Systems, and Applications, 2009. VLSI-TSA ‘09. International Symposium on , vol., no., pp.24-25, 27-29 April 2009
Abstract: The dopant and thermal interaction on solid phase epitaxy (SPE) formed SiC has been investigated. We have studied the impact on substitutional carbon concentration ([C]sub) from various thermal steps including low temperature anneal, SiGe epitaxy thermal budget, RTP, and laser anneal (LSA). Regarding the integration scheme for implementing embedded SiC (eSiC) S/D on NMOS performance enhancement, both post-LDD and post-S/D schemes were studied. The higher [C]sub in post-LDD scheme was observed and the S/D dopants were found to enhance the carbon precipitation into interstitial with conventional RTP/LSA activation thermal processes. The phosphorous implant is also found to degrade [C]sub in comparison to As implant. The higher [C]sub and proximity to channel of formed eSiC in post-LDD scheme are beneficial to device performance. The fabricated eSiC S/D NMOS shows 31% mobility improvement and 7% current enhancement.
URL: http://ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=5159275&isnumber=5159260

2008 IEDM
Yang, B.; Takalkar, R.; Ren, Z.; Black, L.; Dube, A.; Weijtmans, J.W.; Li, J.; Johnson, J.B.; Faltermeier, J.; Madan, A.; Zhu, Z.; Turansky, A.; Xia, G.; Chakravarti, A.; Pal, R.; Chan, K.; Reznicek, A.; Adam, T.N.; de Souza, J.P.; Harley, E.C.T.; Greene, B.; Gehring, A.; Cai, M.; Aime, D.; Sun, S.; Meer, H.; Holt, J.; Theodore, D.; Zollner, S.; Grudowski, P.; Sadana, D.; Park, D.-G.; Mocuta, D.; Schepis, D.; Maciejewski, E.; Luning, S.; Pellerin, J.; Leobandung, E., “High-performance nMOSFET with in-situ phosphorus-doped embedded Si:C (ISPD eSi:C) source-drain stressor,” Electron Devices Meeting, 2008. IEDM 2008. IEEE International , vol., no., pp.1-4, 15-17 Dec. 2008
Abstract: For the first time, embedded Si:C (eSi:C) was demonstrated to be a superior nMOSFET stressor compared to SMT or tensile liner (TL) stressors. eSi:C nMOSFET showed higher channel mobility and drive current over our best poly-gate 45 nm-node nMOSFET with SMT and tensile liner stressors. In addition, eSi:C showed better scalability than SMT plus tensile liner stressors from 380 nm to 190 nm poly-pitches.
URL: http://ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=4796611&isnumber=4796592

2008 EDL
Verheyen, P.; Machkaoutsan, V.; Bauer, M.; Weeks, D.; Kerner, C.; Clemente, F.; Bender, H.; Shamiryan, D.; Loo, R.; Hoffmann, T.; Absil, P.; Biesemans, S.; Thomas, S.G., “Strain Enhanced nMOS Using In Situ Doped Embedded $hbox{Si}_{1 – x}hbox{C}_{x}$ S/D Stressors With up to 1.5% Substitutional Carbon Content Grown Using a Novel Deposition Process,” Electron Device Letters, IEEE , vol.29, no.11, pp.1206-1208, Nov. 2008
Abstract: This letter reports on the implementation of high carbon content and high phosphorous content Si1-xCx layers in the source and drain regions of n-type MOSFET in a 65-nm-node integration scheme. The layers were grown using a novel epitaxial process. It is shown that by implementing stressors with x ap 0.01, nMOSFET device performance is enhanced by up to 10%, driving 880 muA/mum at 1-V V DD. It is also demonstrated that the successful implementation of Si1-xCx relies on the careful choice of integration and epitaxial layer parameters. There is a clear impact of the postepitaxial implantation and thermal treatment on the retained substitutional C content ([C sub]). Furthermore, adding a Si capping layer on top of the Si1 -xCx, greatly improves upon the stressors’ stability during the downstream processing and the silicide sheet resistance.
URL: http://ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=4655506&isnumber=4655490

2008 VLSI
Zhibin Ren; Pei, G.; Li, J.; Yang, B.F.; Takalkar, R.; Chan, K.; Xia, G.; Zhu, Z.; Madan, A.; Pinto, T.; Adam, T.; Miller, J.; Dube, A.; Black, L.; Weijtmans, J.W.; Yang, B.; Harley, E.; Chakravarti, A.; Kanarsky, T.; Pal, R.; Lauer, I.; Park, D.-G.; Sadana, D., “On implementation of embedded phosphorus-doped SiC stressors in SOI nMOSFETs,” VLSI Technology, 2008 Symposium on , vol., no., pp.172-173, 17-19 June 2008
Abstract: We report a successful implementation of epitaxially grown Phosphorus-doped (P-doped) embedded SiC stressors into SOI nMOSFETs. We identify a process integration scheme that best preserves the SiC strain and minimizes parasitic resistance. At a substitutional C concentration (Csub) of ~1.0%, high performance nFETs with SiC stressors demonstrate ~9% enhanced Ieff and ~15% improved Idlin against the well calibrated control devices. It is found that the tensile liner technique provides further performance improvement for nFETs with SiC stressors, whereas the stress memory technique (SMT) does not provide performance gain in a laser annealing process that is used to preserve SiC strain. The material quality of the SiC stressors strongly affects strain transfer.
URL: http://ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=4588607&isnumber=4588540

2005 IEDM
Kah-Wee Ang; King-Jien Chui; Bliznetsov, V.; Yihua Wang; Lai Yin Wong; Chih-Hang Tung; Balasubramanian, N.; Ming-Fu Li; Ganesh Samudra; Yee-Chia Yeo, “Thin body silicon-on-insulator N-MOSFET with silicon-carbon source/drain regions for performance enhancement,” Electron Devices Meeting, 2005. IEDM Technical Digest. IEEE International , vol., no., pp.497-500, 5-5 Dec. 2005
Abstract: We report a novel strained n-channel transistor structure featuring silicon-carbon (SiC) source and drain (S/D) regions formed on thin body SOI substrate. The SiC material is pseudomorphically grown by selective epitaxy and the carbon mole fraction incorporated is 1%. Lattice mismatch between SiC and Si results in uniaxial tensile strain in the Si channel region which contributes favorably to electron mobility enhancement. Drive current IDsat enhancement of 25% was observed for 90 nm gate length LG transistors, and IDsat enhancement of up to 35% was observed at LG of 70 nm. In addition, drive current enhancement shows dependence on device width and channel orientation. All transistors were formed on (001) SOI substrates. The largest IDsat enhancement is observed for transistors with the [010] channel orientation
URL: http://ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=1609390&isnumber=33791

2004 IEDM
Kah Wee Ang; King Jien Chui; Bliznetsov, V.; Anyan Du; Balasubramanian, N.; Ming Fu Li; Ganesh Samudra; Yee-Chia Yeo, “Enhanced performance in 50 nm N-MOSFETs with silicon-carbon source/drain regions,” Electron Devices Meeting, 2004. IEDM Technical Digest. IEEE International , vol., no., pp. 1069-1071, 13-15 Dec. 2004
Abstract: This paper reports a novel strained N-channel transistor structure with sub-100 nm gate lengths. The strained N-MOSFET features silicon-carbon (SiC) source and drain (S/D) regions formed by a Si recess etch and a selective epitaxy of SiC in the S/D regions. The carbon mole fraction incorporated is 1.3%. Lattice mismatch of 0.65% between SiC and Si results in horizontal tensile strain and vertical compressive strain in the Si channel region, both contributing to substantial electron mobility enhancement. The conduction band offset Ec between the SiC source and the strained-Si channel also contributes to increased electron injection velocity from the source. Implementation of the SiC stressors provides significant drive current IDS enhancement in the N-MOSFETs. IDS enhancement of 50% was observed for a gate length of 50 nm.
URL: http://ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=1419383&isnumber=30682

High-performance nMOSFET with in-situ Phosphorus-doped embedded Si:C (ISPD eSi:C) source-drain stressor (B.Yang, AMD/IBM, 2008 IEDM)

Yang, B.; Takalkar, R.; Ren, Z.; Black, L.; Dube, A.; Weijtmans, J.W.; Li, J.; Johnson, J.B.; Faltermeier, J.; Madan, A.; Zhu, Z.; Turansky, A.; Xia, G.; Chakravarti, A.; Pal, R.; Chan, K.; Reznicek, A.; Adam, T.N.; de Souza, J.P.; Harley, E.C.T.; Greene, B.; Gehring, A.; Cai, M.; Aime, D.; Sun, S.; Meer, H.; Holt, J.; Theodore, D.; Zollner, S.; Grudowski, P.; Sadana, D.; Park, D.-G.; Mocuta, D.; Schepis, D.; Maciejewski, E.; Luning, S.; Pellerin, J.; Leobandung, E., “High-performance nMOSFET with in-situ phosphorus-doped embedded Si:C (ISPD eSi:C) source-drain stressor,” Electron Devices Meeting, 2008. IEDM 2008. IEEE International , vol., no., pp.1-4, 15-17 Dec. 2008

Abstract: For the first time, embedded Si:C (eSi:C) was demonstrated to be a superior nMOSFET stressor compared to SMT or tensile liner (TL) stressors. eSi:C nMOSFET showed higher channel mobility and drive current over our best poly-gate 45 nm-node nMOSFET with SMT and tensile liner stressors. In addition, eSi:C showed better scalability than SMT plus tensile liner stressors from 380 nm to 190 nm poly-pitches.

URL: http://ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=4796611&isnumber=4796592

  1. eSiC ~1.8% with in-situ P doping improves Ion as much as 32% due to enhanced tensile stress from SiC
  2. When eSiC S/D becomes thicker more than 30nm from the original surface, effect from tensile stress liner becomes much less.
  3. eSiC strain effect is more compatible with scaled pitch than SMT or TL
  4. structural and electrical connectivity at the junction point between eSiC and extension is important to improve eSiC effect.
  5. Shallow junction with high extension dose makes the connection worse, so that Ion improvement from eSiC is minimal.

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To date, only a few groups have
reported positive progress in introducing eSi:C in thickoxide
long-channel nMOSFET (Ion>20%) [1,2], while little
benefit was achieved with thin-oxide short-channel
nMOSFET (Ion<6%) [1,3]. In fact, all reported thin-oxide
short-channel eSi:C nMOSFET suffered Ion degradation
compared to Si control nMOSFET with SMT and tensile
liner stressors [1, 3-5, table-I].

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Fig.1 shows the typical cross-sectional TEM images of 45 nmnode
nMOSFET transistors with in-situ phosphorus-doped
(ISPD) epitaxial Si:C embedded in the S/D regions. The defect
density of the ISPD eSi:C is found to be acceptably low after
both epitaxial growth (a) and device fabrication up to first
metal (M1) (b).

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Carbon and Phosphorus profiles characterized
by SIMS (Fig.2) showed chemical Carbon atomic
concentration of ~1.9%, and Phosphorus chemical
concentration of ~ 3E20cm-3. An in-line ìXRD technique was
used to monitor the eSi:C film strain (Fig.3) after each
critical processing steps. The effective substitutional C% in
eSi:C was found increased from 1.67% post epitaxial growth
to 1.85% post device fabrication. The increase in eSi:C film
strain was mainly resulted from the high temperature Laser
Annealing (LSA) post EPI growth.

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Fig.6 show that eSi:C flush fill
creates over 2× channel stress compared to 1.2 GPa TL, and
>0.5GPa more stress with 30nm overfill. Additionally, eSi:C
overfill reduces the TL effect, indicating TL becomes much
less effective when eSi:C EPI is 30nm-overfilled.

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The Ioff –
Ion plots (Fig.10) demonstrate that the 30nm-overfilled
eSi:C+TL resulted in the highest drive current, showing ~
32% Ion benefit over the Si control with NL, and ~9% Ion
benefit over the state-of-the-art 45nm-node Si control with
STM+TL stressors. eSi:C could be superior even compared
to the combination of SMT+TL.

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eSi:C showed better scalability (Fig.15), with
only ~1% Ion degradation from 380nm to 190nm pitch (c.f.
Si control, ~5% degradation).

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Rext (Fig.16) and Ion (Fig.17) of the
eSi:C devices varied substantially (Delta_Rext~250 ohm um,
Delta_Ion ~48%).
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ISPD eSi:C
epitaxial-growth-process sensitivity to extension doping
concentrations. Superior structural and electrical connections
between ISPD-eSi:C to nMOSFET extensions (Fig.19) are
easier to establish with device that has low extension doping
concentration (such as our thick-oxide device) than that with
ultra-shallow-junction and extremely high extension doping
concentration (such as our thin-oxide device). Therefore, it
is much more difficult to enable eSi:C with thin-oxide than
that with thick-oxide devices as reported earlier