Summary

חד שכבתי לתקשר סימום של משטחי סיליקון וNanowires שימוש בתרכובות זרחן אורגניות

Published: December 02, 2013
doi:

Summary

A detailed procedure for surface doping of Silicon interfaces is provided. The ultra-shallow surface doping is demonstrated by using phosphorus containing monolayers and rapid annealing process. The method can be used for doping of macroscopic area surfaces as well as nanostructures.

Abstract

חד שכבתי לתקשר סימום (MLCD) הוא שיטה פשוטה לסימום של משטחים וננו 1. MLCD התוצאה היא היווצרות של מבוקר מאוד, רדוד במיוחד ופרופילי סימום חדים בקנה המידה ננומטרי. בתהליך MLCD מקור dopant הוא monolayer המכיל אטומים dopant.

במאמר זה נוהל מפורט לסימום פני השטח של מצע סיליקון, כמו גם nanowires סיליקון בא לידי ביטוי. מקור dopant זרחן הוקם באמצעות monolayer methylenediphosphonate tetraethyl על מצע סיליקון. monolayer זה המכיל מצע הובא למגע עם מצע וטהור פנימי סיליקון יעד ובזמן שיתחשל במגע. התנגדות גיליון של מצע היעד נמדדה באמצעות בדיקה 4 נקודות. nanowires סיליקון הפנימי היו מסונתז על ידי תהליך שיקוע כימי (CVD) באמצעות מנגנון אד נוזל מוצק (VLS); חלקיקי זהב שימשו כזרז לצמיחת nanowire. Nanowires הושעו באתנול על ידי sonication קל. השעיה זו שימשה לdropcast nanowires על מצע סיליקון עם שכבה עליונה דיאלקטרי סיליקון ניטריד. nanowires אלה היו מסוממים בזרחן בצורה דומה לזו המשמשת לפרוסות סיליקון הפנימיות. תהליך photolithography סטנדרטי שימש לפברק אלקטרודות מתכת להיווצרות טרנזיסטור nanowire מבוססות אפקט שדה (NW-FET). התכונות חשמליות של מכשיר nanowire נציג נמדדו על ידי מנתח מכשיר מוליכים למחצה ותחנת בדיקה.

Introduction

Controlled surface doping of semiconductor structures with macroscopic areas as well as at the nanoscale is important for advanced semiconductor device architectures such as FinFet2,3, as well as for nanostructure based devices such as nanowire-based sensors and photovoltaics4-7. We recently introduced monolayer contact doping (MLCD) for repeatable, uniform surface doping of silicon interfaces with macroscopic and nanometric dimensions with control over dopant dose and diffusion profile1. An important feature of MLCD is the restriction of monolayer formation to a substrate that is termed "donor substrate". MLCD simplifies some of the process steps required for Monolayer Contact Doping (MLCD) and provides complementary surface doping capabilities8. Once the donor substrate is loaded with the dopant containing monolayer by using self-limiting surface chemistry, the donor substrate is brought to contact with the substrate intended for doping, termed "target substrate", and both substrates are annealed while in contact. During the anneal process, dopant atoms diffuse to both donor and target substrates, and are activated at the elevated temperature. Since MLCD does not require high energy implantation of dopant atoms, no structural damage is caused to the semiconductor lattice during the process and no further anneal step is required. Good control over dopant diffusion is possible by controlling the rapid thermal process parameters. Ultra shallow and uniform dopant diffusion lengths down to a few nanometers are easily achieved. Separation of the monolayer from the process sequence simplifies the process, allow greater control over process parameters and open new possibilities for doping schemes that were not possible by using other methods. Achieving dopant level as high as the solubility limit of phosphorus in silicon is possible by multiple MLCD doping processes applied successively. In summary, traditional doping methods suffer from intrinsic limitations to fabricate ultra-shallow doping profiles. This is because of inherent statistical variations of source concentrations, overall dose and energy distribution, which are inherent to the low implantation energies required for ultra-shallow implantation. MLCD provides a simple means for surface doping, this is the result of the unique features of MLCD relying on the precise control of dopant dose and location at the atomic scale by utilizing robust surface chemistry for generating the dopant source with self-limiting monolayer chemistry formed exclusively at the semiconductor surface.

Protocol

1. Surface Cleaning Prepare acidic piranha solution by mixing 1:3 hydrogen peroxide (30%) and concentrated sulfuric acid. Caution: Piranha solutions are extremely strong and dangerous oxidizing agents and should be used with extreme caution. These solutions may explode in contact with organic solvents. Only qualified personnel with appropriate training and safety equipment may perform the procedure. Place substrates (later used as donor and target substrates) in appropriate h…

Representative Results

Representative results for phosphorous-MLCD surface doping process are shown in Figure 1. Intrinsic silicon wafers were treated with phosphorous-MLCD, resulting in monotonic decrease in the sheet resistance values. Sheet resistance values decrease for longer anneal times and higher anneal temperatures as shown by the three traces in Figure 1. Sheet resistance values can be correlated to activated dopant concentration. Lower sheet resistance values indicate higher doping levels and vice v…

Discussion

MLCD is a simple and reproducible method. However, attention to surface cleaning and monolayer formation must be taken. Piranha cleaning of the surfaces prior to the MLCD process is important not only for the purpose of avoiding possible impurities, but also for initialization of the surface for reproducible monolayer formation providing reproducible results between processes. The piranha treatment results in hydroxylation of surface groups which is required for binding of precursor molecules to the surface for the forma…

Divulgaciones

The authors have nothing to disclose.

Acknowledgements

This work was partially funded by the Farkas center for light-induced processes.

Materials

High purity silicon wafers Topsil
50 nm Si3N4/50 nm SiO2/Si wafers Silicon Valley Microelectronics
Sulfuric Acid 98% BioLab 19550523
Hydrogen Peroxide 30% J.T. Baker 2190-03
Ammonium Hydroxide 25% J.T. Baker 6051
Ethanol J.T. Baker 8025
Mesitylene Sigma M7200
Dichloromethane Macron 4881-06
Tetraethyl methylenediphosphonate Aldrich 359181
Mineral Oil Sigma M3516
Hydrofluoric Acid 49% J.T. Baker 9564-06
Isopropanol J.T. Baker 9079-05
N-Methyl-2-pyrrolidone J.T. Baker 9397-05
AZ nLOF2020 AZ Electronic Materials nLOF 2020
AZ 726 MIF AZ Electronic Materials 726 MIF
Poly-L-Lysine solution Sigma P8920
Gold colloid solution Ted Pella 82160-80
RTA system AnnealSys MicroAS
4 point probe sheet resistance measurement system Jandel RM3-AR
Mask aligner Suss MA06
e-Beam evaporator VST  TFDS-141E
Semiconductor analyzer Agilent B1500A
CVD system Home-built

Referencias

  1. Hazut, O., Agarwala, A., et al. Contact doping of silicon wafers and nanostructures with phosphine oxide monolayers. ACS Nano. 6 (11), 10311-10318 (2012).
  2. Hisamoto, D., Lee, W. -. C. FinFET- A self-aligned double-gate MOSFET scalable to 20 nm. IEEE Trans. Electron Devices. 47, 2320-2325 (2000).
  3. Leung, G., Chui, C. O. Variability impact of random dopant fluctuation on nanoscale junctionless FinFETs. IEEE Electron Device Lett. 33, 767-769 (2012).
  4. Ho, J. C., Yerushalmi, R., et al. Wafer-scale, sub-5 nm junction formation by monolayer doping and conventional spike annealing. Nano Lett. 9 (2), 725-730 (2009).
  5. Peercy, P. S. The Drive to Miniaturization. Nature. 406, 1023-1026 (2000).
  6. Lu, W., Lieber, C. M. Semiconductor Nanowires. J. Phys. D. 39, R387-R406 (2006).
  7. Gunawan, O., Wang, K., Fallahazad, B., Zhang, Y., Tutuc, E., Guha, S. High Performance Wire-Array Silicon Solar Cells. Prog. Photovoltaics. 19, 307-312 (2011).
  8. Ho, J. C., Yerushalmi, R., Jacobson, Z. A., Fan, Z., Alley, R. L., Javey, A. Controlled nanoscale doping of semiconductors via molecular monolayers. Nat. Mater. 7, 62-67 (2008).
  9. Koren, E., Rosenwaks, Y., Allen, J. E., Hemesath, E. R., Lauhon, L. J. Nonuniform. Doping distribution along silicon nanowires measured by kelvin probe force microscopy and scanning photocurrent microscopy. Appl. Phys. Lett. 95, 092105 (2009).
  10. Wagner, R. S., Ellis, W. C. The vapor-liquid-solid mechanism of crystal growth and its application to silicon. Trans. Metall. Soc. AIME. 233, 1053-1064 (1965).
  11. Cui, Y., Lauhon, L. J., Gudiksen, M. S., Wang, J., Lieber, C. M. Diameter-controlled synthesis of single-crystal silicon nanowires. Appl. Phys. Lett. 78 (15), 2214-2216 (2001).

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Hazut, O., Agarwala, A., Subramani, T., Waichman, S., Yerushalmi, R. Monolayer Contact Doping of Silicon Surfaces and Nanowires Using Organophosphorus Compounds. J. Vis. Exp. (82), e50770, doi:10.3791/50770 (2013).

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