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Taheri P, Fahad HM, Tosun M, et al. Nanoscale Junction Formation by Gas-Phase Monolayer Doping. ACS Appl Mater Interfaces. 2017;9(24):20648-20655doi: 10.1021/acsami.7b03974.
Taheri, P., Fahad, H. M., Tosun, M., Hettick, M., Kiriya, D., Chen, K., & Javey, A. (2017). Nanoscale Junction Formation by Gas-Phase Monolayer Doping. ACS applied materials & interfaces, 9(24), 20648-20655. https://doi.org/10.1021/acsami.7b03974
Taheri, Peyman, et al. "Nanoscale Junction Formation by Gas-Phase Monolayer Doping." ACS applied materials & interfaces vol. 9,24 (2017): 20648-20655. doi: https://doi.org/10.1021/acsami.7b03974
Taheri P, Fahad HM, Tosun M, Hettick M, Kiriya D, Chen K, Javey A. Nanoscale Junction Formation by Gas-Phase Monolayer Doping. ACS Appl Mater Interfaces. 2017 Jun 21;9(24):20648-20655. doi: 10.1021/acsami.7b03974. Epub 2017 Jun 07. PMID: 28548483.
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ACS Appl Mater Interfaces. 2017 Jun 21;9(24):20648-20655. doi: 10.1021/acsami.7b03974. Epub 2017 Jun 07.

Nanoscale Junction Formation by Gas-Phase Monolayer Doping.

ACS applied materials & interfaces

Peyman Taheri, Hossain M Fahad, Mahmut Tosun, Mark Hettick, Daisuke Kiriya, Kevin Chen, Ali Javey

Affiliations

  1. Electrical Engineering and Computer Sciences, University of California , Berkeley, California 94720, United States.
  2. Berkeley Sensor and Actuator Center, University of California , Berkeley, California 94720, United States.
  3. Materials Sciences Division, Lawrence Berkeley National Laboratory , Berkeley, California 94720, United States.

PMID: 28548483 DOI: 10.1021/acsami.7b03974

Abstract

A major challenge in transistor technology scaling is the formation of controlled ultrashallow junctions with nanometer-scale thickness and high spatial uniformity. Monolayer doping (MLD) is an efficient method to form such nanoscale junctions, where the self-limiting nature of semiconductor surfaces is utilized to form adsorbed monolayers of dopant-containing molecules followed by rapid thermal annealing (RTA) to diffuse the dopants to a desired depth. Unlike ion implantation, the process does not induce crystal damage, thus making it highly attractive for nanoscale transistor processing. To date, reported MLD processes have relied on solution processing for monolayer formation. Gas-phase processing, however, benefits from higher intra- and interwafer uniformity and conformal coverage of 3D structures and is more desirable for manufacturing. In this regard, we report a new approach for MLD in silicon and germanium using gas-phase monolayer formation. We call this technology gas-phase monolayer doping (GP-MLD). This method relies on sequential pulse-purge cycles of gas-phase dopant-containing molecules to form a boron- or phosphorus-containing monolayer on a target semiconductor surface. Here, we show the feasibility of our approach through the formation of ultrashallow B- and P-doped junctions on Si and Ge surfaces. The mechanism of adsorption is characterized using Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. Sub-5 nm junction depths with high dopant dose are obtained as characterized by secondary ion mass spectrometry and sheet resistance measurements. Additionally, we demonstrate that area selectivity can be achieved via lithographic patterning of the monolayer dopants before the diffusion step. The results demonstrate the versatility of the GP-MLD approach for formation of controlled and ultrashallow junctions.

Keywords: area-selective doping; gas-phase monolayer doping; molecular adsorption; nanoscale junction; rapid thermal annealing

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