M. Juhel

Three dimensional distributions of arsenic and platinum within NiSi contact and gate of an n-type transistor

Atom probe tomography was used to study the redistribution of platinum and arsenic atoms after Ni(Pt) silicidation of As-doped polycrystalline Si. These measurements were performed on a field-effect transistor and compared with those obtained in unpatterned region submitted to the same process. These results suggest that Pt and As redistribution during silicide formation is only marginally influenced by the confinement in microelectronic devices. On the contrary, there is a clear difference with the redistribution reported in the literature for the blanket wafers. Selective etching used to remove the non-reacted Ni(Pt) film after the first rapid heat treatment may induce this difference.

Low-Temperature Low-Resistivity PEALD TiN Using TDMAT under Hydrogen Reducing Ambient

Titanium nitride (TiN) films were deposited using plasma-enhanced atomic layer deposition (PEALD) from the organometallic precursor tetrakis-dimethyl-amino-titanium (TDMAT) with hydrogen (H 2 ) as a coreactant. Low-resistivity values lying from 210 to 275 μΩ cm were achieved for 10 nm thick films deposited at low temperature: 150°C. The effects of temperature, plasma time, and plasma power were investigated. It was demonstrated that the chemical reaction is complementary and self-limiting. A minimum energy is necessary to reach the low-resistivity plateau. Chemical and physical properties of the films are also reported and a surface reaction mechanism is proposed. It is suggested that after TDMAT chemisorption to the surface, amines are removed by hydrogen radicals, and at the same time, titanium carbide bonds (Ti-C) are formed. The low resistivity results from the presence of Ti 2 C or Ti 2 N phases in the PEALD TiN film. The industrial viability of this process was also evaluated on 300 mm wafers. Good performances were obtained on wafer-to-wafer uniformity and step coverage, while some improvements related to the within-wafer uniformity are required.

Two-dimensional quantitative mapping of arsenic in nanometer-scale silicon devices using STEM EELS―EDX spectroscopy

Field emission gun (FEG) nanoprobe scanning electron transmission microscopy (STEM) techniques coupled with energy dispersive X-ray (EDX) and electron energy loss spectroscopy (EELS) are evaluated for the detection of the n-type dopant arsenic, in silicon semiconductor devices with nanometer-scale. Optimization of the experimental procedure, data extraction and the signal-to-noise ratio versus electron dose, show that arsenic detection below 0.1% should be possible. STEM EDX and EELS spectrum profiles have been quantified and compared with secondary ion mass spectrometry (SIMS) analyses which show a good agreement. In addition, the arsenic doping level found inside large and small epitaxial devices have been compared using STEM EDX-EELS profiling. The average doping level is found to be similar but variable interface segregation has been observed. Finally, STEM EDX arsenic mapping acquired in a BiCMOS transistor cross-section shows strong heterogeneities and segregation in the epitaxially grown emitter part.

Three-dimensional distribution of Al in high-k metal gate: Impact on transistor voltage threshold

The three-dimensional spatial distribution of Al in the high-k metal gates of metal-oxide-semiconductor field-effect-transistors is measured by atom probe tomography. Chemical distribution is correlated with the transistor voltage threshold (VTH) shift generated by the introduction of a metallic Al layer in the metal gate. After a 1050 °C annealing, it is shown that a 2-A thick Al layer completely diffuses into oxide layers, while a positive VTH shift is measured. On the contrary, for thicker Al layers, Al precipitation in the metal gate stack is observed and the VTH shift becomes negative.

STEM EDX applications for arsenic dopant mapping in nanometer scale silicon devices

In this paper we evaluate sensitivity limits and applications of scanning transmission electron microscopy (STEM) energy-dispersive X-ray (EDX) spectroscopy technique for the mapping of arsenic dopant distribution in nanometer range silicon devices. First we show that lamella radiation damages, generated by the intense focused electron probe at 200 keV, are significantly reduced at 120 keV. This allows to use high electron doses and therefore to improve the EDX sensitivity. The analysis of 45nm nMOS transistor clearly shows the n doped areas and local segregation in gate and spacers.

Shallow junction engineering by Phosphorus and Carbon co-implantation: optimization of Carbon dose and energy

optimization of Carbon dose and energy Nathalie Cagnat, Cyrille Laviron, Daniel Mathiot, Chris Rando, Marc Juhel, Julien Singer, Frederic Salvetti, Christophe Wyon, Kelkun Duteme STMicroelectronics, 850 rue Jean Monnet, 38926 Crolles cedex, France NXP, 850 rue Jean Monnet, 38926 Crolles cedex, France Freescale, 850 rue Jean Monnet, 38926 Crolles cedex, France InESS, 23 rue du Loess, BP 20 CR, 67037 Strasbourg cedex 2, France LETI, CEA-Grenoble, 17 rue des Martyrs, 38054 Grenoble cedex 9, France

Elimination of Post Cu-CMP Watermark by Optimizing Post CMP Clean to Control Cu Dissolution

No watermarks are detected for 1000A of initial cap thickness. Between 400 and 600 A, the density of watermark is multiplied by a factor 10. The increase in watermark with the decrease of the initial cap thickness is explained by a larger low-k film area exposure. In particular, patterned structures with higher metal density will be more eroded because of the increased amount of in-between metal lines dielectric consumption. Auger analysis of the watermark indicates that defects consist of Cu precipitate likely originating from the post-CMP clean step.

Boron atomic-scale mapping in advanced microelectronics by atom probe tomography

Two types of industrial transistor technologies have been studied using atom probe tomography (APT). Both 14 nm node high-K metal-oxide-semiconductor field effect transistors (MOSFETs) on ultrathin body and buried oxide and 320 GHz Ft Si/SiGe Heterojunction Bipolar Transistors (HBT) embedded in a 55-nm BiCMOS chip have been analysed and their atomic distribution has been mapped. Due to the limitations of routine characterisation techniques, boron can remain invisible in such nanometric sized structures. Also, size effects can induce differences between the actual device and larger test zones used for monitoring these technologies. This paper presents results obtained by APT from two advanced nodes, in contrast to complementary techniques. Using different methodologies, including specific APT-friendly test structures and multiple-impact data filtering, the dopant behaviour in these structures can be better understood. An unexpected boron distribution in both the MOSFET source/drain and HBT base regions has been highlighted.Two types of industrial transistor technologies have been studied using atom probe tomography (APT). Both 14 nm node high-K metal-oxide-semiconductor field effect transistors (MOSFETs) on ultrathin body and buried oxide and 320 GHz Ft Si/SiGe Heterojunction Bipolar Transistors (HBT) embedded in a 55-nm BiCMOS chip have been analysed and their atomic distribution has been mapped. Due to the limitations of routine characterisation techniques, boron can remain invisible in such nanometric sized structures. Also, size effects can induce differences between the actual device and larger test zones used for monitoring these technologies. This paper presents results obtained by APT from two advanced nodes, in contrast to complementary techniques. Using different methodologies, including specific APT-friendly test structures and multiple-impact data filtering, the dopant behaviour in these structures can be better understood. An unexpected boron distribution in both the MOSFET source/drain and HBT base regions has...

3D Atomic Scale Analysis of CMOS type structures for 14 nm UTBB-SOI technology

As the dimensions of microelectronic devices are progressively reduced new architectures and materials are being introduced to try and meet ever stricter performance criteria. The use of high-k dielectrics (hafnium based oxides) can reduce leakage current leading to better electrical properties. The coupling of these dielectrics with metallic gate materials (TiN) has led to structures of greater complexity in CMOS (complementary metal oxide semiconductor) devices. Due to current dimensions (a few nanometres) atom probe tomography (APT) is one of the very few techniques which can give 3D chemical information at this scale [1-2]. But due to the insulating and high evaporation field nature of these materials analysis is often difficult, with very low analysis yields, or even impossible [3].

Copper Surface Analysis with ToF-SIMS: Spectra Interpretation and Stability Issues

In integrated circuit manufacturing, surface cleanliness is mandatory to achieve high production volumes and device yield. Time-Of-Flight Mass Spectroscopy (ToF-SIMS) is an attractive technique for contamination control since it does provide information about both elemental and molecular species present on essentially any surface and offers high chemical sensitivity associated with sub-micrometer range spatial resolution and short acquisition time. The benefits of this technique to control surfaces after post copper chemical mechanical polishing (Cu-CMP) cleaning [1, 2] and after post via etch cleaning have already been reported.