Controlled atomic scale fabrication based on scanning probe patterning or surface assembly typically involves a complex process flow, stringent requirements for an ultra-high vacuum environment, long fabrication times and, consequently, limited throughput and device yield. We demonstrate a device platform that overcomes these limitations by integrating scanning-probe based dopant device fabrication with a CMOS-compatible process flow. Silicon on insulator substrates are used featuring a reconstructed Si(001):H surface that is protected by a capping chip and has pre-implanted contacts ready for scanning tunneling microscope (STM) patterning. Processing in ultra-high vacuum is thereby reduced to a few critical steps. Subsequent reintegration of the samples into the CMOS process flow opens the door to successful application of STM fabricated dopant devices in more complex device architectures. Full functionality of this approach is demonstrated with magnetotransport measurements on degenerately doped STM patterned Si:P nanowires up to room temperature.

Ultra-high vacuum (UHV) investigations have demonstrated a successful development of atomic nanostructures. The scanning tunneling microscope (STM) provides surface study at the atomic scale. However, the surface preparation is a crucial experimental step and requires a complex protocol conducted in situ in a UHV chamber. Surface contamination, atomic roughness, and defect density must be controlled in order to ensure the reliability of advanced UHV experiments. Consequently, a packaging for nanoscale devices has been developed in a microelectronic clean room environment enabling the particle density and contaminant concentration control. This nanopackaging solution is proposed in order to obtain a Si(001)-(2×1):H reconstructed surface. This surface is protected by a temporary silicon cap. The nanopackaging process consists in a direct bonding of two passivated silicon surfaces and is followed by a wafer dicing step into 1-cm2 dies. Samples can be stored, shipped, and in situ opened without any additional treatment. A specific procedure has been developed in order to open the nanopackaged samples in a UHV debonder, mounted in the load-lock chamber of a low-temperature STM system (LT-STM). Statistical large scan LT-UHV-SEM images and LT-UHV-STM images have been obtained enabling the surface study at the atomic resolution.

Based on their nanoscale size and morphology, as well as on their auto-assembling properties, bio-inspired nano-objects have been identified as potential interconnection and sensor materials. Their electrical properties, namely conduction mechanism and electrical contact, have to be studied in order to enable a comparison with standard microelectronic components. In this paper, a generic characterization platform for bio-inspired nano-objects is proposed, enabling electrical investigations ranging from dry electrical measurements to wet electrochemical investigation, and for bio-inspired materials morphologies from single nanowires to films. Various electrode patterns have been designed and fabricated on 200mm silicon substrates, before being diced at chip scale and embedded in easy-to-plug systems for dry and wet measurements, including climatic chamber or glove box. Fully biocompatible microelectronic fabrication processes have been selected.

With their attractive intrinsic properties, such as morphology, autoassembling properties, and tailorability, nano-objects could provide alternative and innovative routes to current microelectronics and nanoelectronics. Further insight on their electrical properties, especially in terms of statistics and reproducibility, as well as on their potential integration into silicon-based electronics is, however, often required to be able to fully exploit their potential. This paper proposes an innovative approach using a generic structure allowing the study of nano-objects electrical properties. Regarding the nano-objects integration, a homogeneous approach is presented with the in situ fabrication of atomic wires as a possible planar interconnection system. A heterogeneous approach is described as well with the characterization and preliminary integration of biological material, such as deoxyribonucleic acid-based nanowires or amyloid fibers.

Microelectronics industry aims at pushing the scaling of MOSFET devices, with a lot of challenges to solve for front-end and back-end processes. These challenges are also new opportunities, as for co-integration between silicon components and biological objects. In particular, bio-inspired nano objects such as DNA-based nanowires and protein-based nanowires have generated a huge interest based on their promising electrical properties [1, 2] and their size at the nanoscale. They could indeed bring a rich evolution in the nanotechnology community. This paper presents a common work performed by microelectronic biology and characterization teams which aims at describing the design, and the fabrication of a characterization platform dedicated to bio-inspired objects, and the first electrical measurements acquired on amyloid fibers. The design of this characterization platform takes into account biological and microelectronic constraints. Regarding biological constraints, special attention has been paid to materials choice and device fabrication in order to be biocompatible and to enable drop deposition for both wet and dry experiments. Dedicated patterns have been designed in order to measure electrical parameters such as contact resistance and resistivity of the bio-inspired objects. Regarding the fabrication step, the characterization platform has taken advantage from microelectronic technologies, especially in terms of size (nanoscale), reproducibility and robustness taken into account the specific environment. These aspects will be further discussed in this paper, as well as the first electrical measurements. To properly understand the electrical characteristics of bio-inspired objects, one critical point is the measurement of the linear conductivity of these objects, which implies the discrimination from contact resistance. Another important point is the conduction mechanism. Table 1 presents two patterns used to investigate the conduction mechanisms. To realize a complete electrical study, we have thus decided to design specific test structures as Transmission Line Matrix (TLM) and Van der Pauw patterns, structures with a variable electrode gap, and different contact areas structures. Figure 1 shows SEM images of the electrodes fabricated with this specific layout. The inter-electrode distance has been measured at 1µm and 70µm x 70µm square pads have been obtained. The figure 2 presents a cross section view of the fabricated electrodes. Electrode thickness is equal to 200nm and the width is equal to 1.7µm. Material impact and electrochemical properties of bio-inspired objects have also been investigated. Working with biological object at the nanoscale requires further restrictions. The main constraint is the use of biocompatible material to pattern all the layers in contact with the bio-inspired object. We have decided to use (i) platinum and gold because these metals are commonly used in biological measurements, and (ii) ruthenium due to its anisotropic etching properties. Another requirement relies on back gate electrode to enable the field effect investigation of bio-inspired object. To deal with wet measurement and to control the film deposition at the desirable position we have decided to engineer further cavities. Regarding packaging solutions, standard microelectronic metallic pads have been patterned to allow automated electrical characterization. Bioelectrical investigations as electrochemistry or control atmosphere measurements require the design of an “easy to plug” device enabling drop deposition and a very simple electrical connection adapted to electrical probers. This “easy to plug” device has been fabricated including a patterned silicon die assembled with a conductive glue on a Side-brazed Ceramic Dual In-inline Package (SCDIP) and wire-bonding. A SCDIP has been especially chosen to be easily carried and plugged inside biological equipment such as climatic chamber and glove box. Large package have been used in order to connect the maximum of patterns but also to provide an important protein-based nanowires density on the top of the electrodes. Figure 3 presents photography picture of the characterization platform used to perform the conduction measurements in biological equipment. The figure 4 presents the first electrical signal of the bio-inspired nano object which confirms that the characterization platform has been correctly fabricated and can be able to study the electrical properties of the protein film. This papers aims at presenting more details on (i) the design, (ii) the fabrication of silicon die in clean room (iii) the packaging adapted to the biological environment and (iv) results of electrical characterization of the bio-inspired objects at the nanoscale. References [1] D. V. Lim, M. M. Simpson, E. A. Kearns et al., Clin. Microbiol. Rev., vol. 18, no. 4, pp. 583–607, Oct. 2005. [2] F. S. Ligler and J. S. Erickson, Nature, vol. 440, no. 7081, pp. 159–160, Mar. 2006. Figure 1

This paper proposes an extensive analysis of the impact of both structural effect and charge parameters on silicon nanowire-based biological sensors, for single-charge detection. These parameters are calibrated on physical and electrical characterizations and are subsequently introduced in a compact model to predict the signal over noise ratio (SNR). We finally propose rules for the design of nanowires and recommendations for the placement of the biological element, inducing the single charge release.

In the wide range of emergent nanotechnologies, DNA-based microelectronics has shown an important potential for components miniaturization and auto-assembling approaches applicable to future silicon-based electronic circuits [1]. In order to pursue the Moore's law, interconnections must be indeed addressed at the nanoscale, with a good control of their size, location and electrical & thermal performances. With its natural auto-assembling property, its 2-nm-double-helix diameter and its several metallization possibilities, DNA is a promising candidate to build bio-inspired electronic components [1]. DNA has been first metallized by Erez Braun in 1998 using a silver electroless method [2]. Since 1998, several groups have worked on DNA metallization using different chemistries with metals such as Pd, Pt, Au, Ag and Cu [3]. Most of these works have presented electrical and morphological characterizations of few metallic nanowires. However, in order to initiate DNA-based-nanowires integration on silicon technologies, we must start to implement nanowires on silicon at wafer scale. We have thus developed a platform based on silicon technologies providing morphological and electrical characterizations of copper nanowires built from DNA [4]. This platform will allow us to simultaneously characterize a large number of nanowires, returning a statistic of their electrical performance, and thus allowing the optimization of the copper nanowire metallization process. Two main approaches are proposed to fabricate and contact a large number of copper nanowires with metallic electrodes in order to study their electrical behavior. In both approaches, a linear 16-μm-length DNA phage is used. The first approach consists in aligning DNA wires on a hydrophobic silicon oxide surface by a method called DNA combing. On a second time, aligned DNA wires are all metallized by electroless process [4]. 5-nm-diameter copper nanowires have been so far achieved by this method and focus on improving the metallization process is currently at stake. Finally, Ti/Au electrodes are fabricated on the nanowires by a classical lift-off process in order to electrically connect them. The advantage of this approach is the very accurate nanowires alignment and their homogeneity over the surface. However, the low number of aligned nanowires per surface unit (10–20μm−2) and the high electrical resistance of each (>kohms) makes the electrical characterization quite complex. On the other side, the second approach consists in fabricating the Ti/Au electrodes first and then aligning or randomly depositing the copper nanowires at their surface. Same protocols are used to align and metallize the DNA nanowires for both approaches. The advantage of this second approach is a higher nanowire density deposited on the electrodes. However, a higher contact resistance and a lower control of nanowires alignment are obtained. Both approaches are currently explored and permit to explore a wide range of parameters for copper nanowires metallization process improvement.

We present our recent developments on silicon technologies dedicated to the packaging of nano-objects/nano-devices. These technologies aim at both protecting and electrically connecting a nanoscale device positioned on a perfect Si(001)-(2 × 1):H surface smoothed thanks to a 950 °C thermal treatment. The nano-device is connected to nanopads implanted on the silicon surface. Each nanopad is linked to a nanovia which is locally achieved by etching and filling processes operated in a FIB (Focused Ion Beam) equipment. Impacts of the FIB process on via morphology and properties are depicted. Nanopads are fabricated through the local implantation of arsenic, and the effect of the surface smoothing thermal treatment on the dopants diffusion length is estimated by simulation and then experimentally explored. Key process steps such as the etching of a deep cavity and the surface protection with a temporary cap are also described, and a first assembly consisting in a substrate equipped with nanopads and directly bonded with a cap substrate is presented.

The last decade, an important effort has been allocated to emergent nanomaterials as an alternative route to current silicon-based technologies in order to face physics issues appearing with the downscaling of electronics components (Moore's law). In this paper, studies on DNA material have been conducted in order to take advantage of both DNA nanoscale and auto-assembling properties. The combination of these two properties is very promising for building a new generation of DNA-based interconnects. However, since the first metallized DNA wire developed by Erez Braun in 1998, one of the major issues met by researchers is the low electrical performances achieved on DNA-based nanowires used as interconnections. In this project, we are developing a statistical approach to determine the electrical properties of metallized DNA nanowires relying upon the deposition and alignment of a large population of nanowires on a silicon substrate equipped with different metallic electrode sets.