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In 0.53 Ga 0.47 As Channel N-MOSFETs with Shallow Metallic S/D Extension
| Content Provider | Semantic Scholar |
|---|---|
| Author | Gong, Xiao Ivana Yeo, Yee-Chia |
| Copyright Year | 2011 |
| Abstract | We report the first demonstration of In0.53Ga0.47As nMOSFETs with a shallow metallic source/drain extension (SDE). A SDE-last process was used: the Ni-InGaAs metallic SDE was formed last, after deep n S/D implant, to achieve self-aligned highly-abrupt SDE junctions. Junction leakage between was effectively suppressed by ~40 times with the deep S/D implant. INTRODUCTION InGaAs n-MOSFETs could potentially replace Si nMOSFETs for logic applications in sub-16 nm technology node [1][7]. InGaAs MOSFETs are more vulnerable to short channel effects (SCE) than Si MOSFETs due to the narrower bandgap and higher permittivity of InGaAs material. Therefore, SCE control in InGaAs MOSFETs is important. Various S/D junction engineering techniques has been shown to reduce SCE, such as ultra-shallow junction formation and anti-punchthrough halo (pocket) implantation [8]-[9]. In this paper, InGaAs MOSFETs with shallow and highlyabrupt metallic SDE were proposed for reduction of SCE. The metallic SDE formation comprises of Ni reaction with InGaAs and selective etch of unreacted excess Ni. A SDE-last process was developed to realize this novel structure. DEVICE FABRICATION Fig. 1 shows the process flow for fabricating an In0.53Ga0.47As N-MOSFET with Ni-InGaAs shallow SDE and deep S/D implant. Key steps are schematically illustrated in Fig. 1(b). In0.53Ga0.47As (thickness of 1 μm, p-type doped at 2×10 cm) on p InP substrates were used for device fabrication. After pre-gate clean, and ex situ passivation using (NH4)2S, the sample was quickly loaded into an atomic layer deposition (ALD) tool for Al2O3 deposition. Post-gate dielectric deposition anneal (PDA) at 400 °C for 60 s was then performed using rapid thermal anneal (RTA). This was followed by the TaN gate electrode deposition and gate stack patterning. Silicon oxynitride (SiON) spacer was formed before deep S/D Si implantation (20 keV, 1×10 cm dose). SiON spacer was removed after a 600°C 60 s dopant activation. 15 nm Ni was sputtered over the whole wafer. A RTA at 250 °C for 60 s was carried out to induce reaction between Ni and InGaAs, forming the Ni-InGaAs S/D extension. Selective etch of unreacted excess Ni using concentrated HCl was done to complete the device fabrication. The Ni-InGaAs serves as both SDE and S/D metal contact. RESULTS AND DISCUSSION Cross-sectional TEM images of a device structure with SiON spacer formed before deep S/D implant are shown in Fig. 2. Fig. 3 shows the TEM image of a completed In0.53Ga0.47As n-MOSFET with shallow Ni-InGaAs SDE. Ni-InGaAs extension as shallow as sub-10 nm can be achieved by precise control of the sputtered Ni thickness. The reaction between Ni and InGaAs involves diffusion of Ni into InGaAs. This enables the integration of Ni-InGaAs SDE. An atomic composition of Ni: In: Ga: As = 43: 12: 16: 29 was detected in the Ni-InGaAs SDE region by energy dispersive X-ray spectroscopy (EDX). Lateral diffusion of Ni-InGaAs under the gate stack was observed. Secondary ion mass spectrometry (SIMs) analysis at the S/D contact region is shown in Fig. 4. The profile of Ni and Si shows that thin Ni-InGaAs layer was formed above the deep S/D implant Si concentration peak position. ID-VG, ID-VD, and extrinsic transconductance Gm,ext -VG plots for a device with 5 μm gate length and 2.5 nm EOT are shown in Fig. 5, 6, 7, respectively. Good transfer and output characteristics were observed. Significant performance enhancement can be expected when integrating this novel structure into short channel device with lower EOT. I-V characteristics of the source-to-body junction of nMOSFETs with Ni-InGaAs SDE were measured. Similar measurements were performed on devices with Ni-InGaAs directly formed on p-InGaAs (as illustrated in Fig. 9). The cumulative probability plot shown in Fig. 8 compares the leakage current density taken at the reverse bias of 1 V. Around 40 times reduction of reverse leakage current density was achieved with the deep S/D implant. Table I compares our proposed novel metallic SDE junction structure with other three different S/D junction structures. MOSFETs with thick Ni-InGaAs contact formed on implanted n type S/D can significantly suppress the off-state leakage current compared to MOSFETs with Ni-InGaAs formed directly on p type InGaAs [10]-[11]. Shallow Ni-InGaAs SDE formed last may be promising for reduction of DIBL in short channel InGaAs MOSFETs. Compared with the conventional short channel devices with lightly doped S/D extension, the novel Ni-InGaAs SDE can achieve a more abrupt SDE junction. CONCLUSION InGaAs n-MOSFETs featuring Ni-InGaAs SDE was proposed and demonstrated by using the SDE-last process for the first time. The deep S/D implant suppresses the source to drain leakage current. Accurate control of the SDE junction abruptness make this novel structure a promising candidate for extremely small scale InGaAs MOSFETs. Acknowledgement. This work is supported by National Research Foundation and Defence Science and Technology Agency, Singapore. REFERENCES [1] M. Radosavljevic et al., IEDM Tech. Dig, pp. 319, 2009. [2] Y. Q. Wu et al., IEDM Tech. Dig., pp. 323, 2009. [3] H.-C. Chin et al., Symp. VLSI Tech. Dig., pp. 244, 2009. [4] H.-J. Oh et al., IEDM Tech. Dig., pp. 339, 2009. [5] X. Gong et al., Jpn. J. Appl. Phy., 2010. [6] M. Yokoyama et al., IEDM Tech. Dig., pp. 46, 2010. [7] X. Gong et al., ECS, pp. 117, 2010. [8] A. Shima et al., Symp. VLSI Tech. Dig., pp. 174, 2004. [9] T. Hori et al., IEDM Tech. Dig., pp. 75, 1994. [10] S. H. Kim et al., IEDM Tech. Dig., pp. 597, 2010. [11] X.-G. Zhang et al., VLSI-TSA, pp. 26, 2011. -580Extended Abstracts of the 2011 International Conference on Solid State Devices and Materials, Nagoya, 2011, pp580-581 A-2-4 |
| File Format | PDF HTM / HTML |
| DOI | 10.7567/SSDM.2011.A-2-4 |
| Alternate Webpage(s) | https://confit.atlas.jp/guide/event-img/ssdm2011/A-2-4/public/pdf_archive?type=in |
| Alternate Webpage(s) | https://doi.org/10.7567/SSDM.2011.A-2-4 |
| Language | English |
| Access Restriction | Open |
| Content Type | Text |
| Resource Type | Article |
