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Whereas the introduction of 3D-dimensional devices such as FINFET's may be a solution for next generation technologies, they do represent significant challenges with respect to the doping strategies and the junction characterization.Aiming at a conformal doping of the source/drain regions in a FINFET in order to induce a conformal under diffusion and homogenous device operation, one can quickly recognize that classical beam implants fail to fulfill these needs, in particular when considering closely spaced fin's. Indeed the effects of different implant angles (top vs bottom) and the concurrent variation in projected range, dose retention and sputtering as well as the effect of the wafer rotation when tilting is used, all lead to a non-conformal doping. Alternative processes such as vapor phase deposition (VPD) or plasma doping are presently being considered, as they hold the promise of conformality. Using VPD or Atomic Layer Doping dopant atoms are deposited on the surface through thermal decomposition of typical chemical vapor deposition precursors and are subsequently in diffused. Good conformality (~ 93 % for sidewall vs. top dose), defect free junctions and high activation levels are the positive points of this process. Plasma immersion doping is an alternative approach which is easier to integrate (similar to ion implantation) and suitable for p-and n-type doping. Whereas it holds the promise of conformality when implanting large macroscopic features, the latter is far less obvious when trying to dope microscopic feature conformally. In fact the formation of conformal junctions in FINFET's with plasma based processes is quite challenging and relies on secondary processes such as resputtering, deposition and in diffusion etc. Their optimization is compromised by concurrent artifacts, sputter erosion being the most important one. In support of these developments the measurement and identification of conformality adequate metrology is required. For this purpose we have extensively used Scanning Spreading Resistance Microscopy (SSRM) as a means to characterize the vertical/lateral junction depths, the concentration levels and the degree of conformality. Characterization of the (3D)-underdiffusion can be achieved by a dedicated SSRM experiment and/or the Tomographic Atomprobe. As a complement to the SSRM technique we also developed a concept based on resistance measurements of fin's which allows to map the sidewall doping across the wafers and provides fast feedback on conformality.

Doping fin field-effect transistor sidewalls : impurity dose retention in silicon due to high angle incident ion implants and the impact on device performance Duffy, R.; Curatola, G.; Pawlak, B.J.; Doornbos, G.; Tak, van der, K.; Breimer, P.; Berkum, van, J.G.M.; Roozeboom, F. Please check the document version of this publication:• A submitted manuscript is the author's version of the article upon submission and before peer-review. There can be important differences between the submitted version and the official published version of record. People interested in the research are advised to contact the author for the final version of the publication, or visit the DOI to the publisher's website.• The final author version and the galley proof are versions of the publication after peer review.• The final published version features the final layout of the paper including the volume, issue and page numbers. Link to publication Citation for published version (APA):Duffy, R., Curatola, G., Pawlak, B. J., Doornbos, G., Tak, van der, K., Breimer, P., ... Roozeboom, F. (2008). Doping fin field-effect transistor sidewalls : impurity dose retention in silicon due to high angle incident ion implants and the impact on device performance. Journal of Vacuum Science and Technology, B: Microelectronics and Nanometer Structures--Processing, Measurement, and Phenomena, 26(1), 402-407. DOI: 10.1116/1.2816925 General rightsCopyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright owners and it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights.• Users may download and print one copy of any publication from the public portal for the purpose of private study or research.• You may not further distribute the material or use it for any profit-making activity or commercial gain • You may freely distribute the URL identifying the publication in the public portal ? Take down policyIf you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim. The three dimensional ͑3D͒ nature of a fin field-effect transistor ͑FinFET͒ structure creates new challenges for an impurity doped region formation. For the triple gate FinFET, both top and side surfaces require high levels of dopant incorporation to minimize access resistance. In this work, we investigate the use of conventional ion implantation for the introduction of impurities in this 3D silicon structure. Specifically, we evaluate sidewall impurity dose retention at various angles of incidence. The retention of dose is determined by ͑i͒ trigonometry of the implant angle in the 3D fin system, ͑ii͒ backscattering, and ͑iii͒ material properties of the target surface. Dose retention is most sensitive to the implant angle. For a fixed implant projected range, lighter ions are more likely to be ejected from the target. Thus, heavier ions are better for...

With emerging three-dimensional device architectures for advanced silicon devices such as fin field-effect-transistors (FinFETs), new metrology challenges are faced to characterize dopants. The ratio of dopant concentration in the top surface and sidewalls of FinFETs may differ significantly, thereby influencing the performance of these devices. In this work, a methodology involving secondary ion mass spectrometry (SIMS) is presented to study the dose conformality in fins. However, SIMS is limited to probe the quantitative chemical dopant concentration (i.e., top/sidewall of fins). The fraction of the active dopant concentration determining the performance of FinFETs would still be unknown. Additionally, the concept based on SIMS is unable to provide information on the lateral junction depth. Thus, to obtain the unknown active dopant concentration and their spatial distribution, the authors extend their study by measuring the cross section of the fins with scanning spreading resistance microscopy and extracting the quantitative active carrier concentration in the fins.

For scaling complementary metal oxide semiconductor devices toward the ITRS goals for the 32nm technology node and beyond, fin shaped field effect transistor (finFET)-based structures have shown immense potential due to their scalability by maintaining high drive current at scaled voltages and smaller gate dimensions. Due to the three-dimensional geometry of finFETs and the need to obtain identical lateral dopant profiles on the top and the sidewall of the fins, the classical doping strategies need to be reengineered as regular beam line implants would lead to large nonconformalities. The development of alternative doping processes such as plasma immersion doping requires the availability of methods to probe doping conformality. A methodology based on a dedicated resistor structure was developed, enabling the use of automated measurements to provide fast feedback on the degree of sidewall doping within different dies, across the wafer, and to study the wafer to wafer variation within a lot containing various splits. The methodology is validated by comparing the results with predictions based on a model describing the varying degree of conformality for beam line implants with different tilt angles.