Interfacing devices fabricated in modern CMOS processes with biological systems is the focus of intense research [1][2][3][4]. The miniaturization trend in the semiconductor industry enables the design of high-density biosensors combined with on-chip mixed signal circuitry for amplification, filtering and analog-to-digital conversion. Many technologies use aluminium as interconnect material which corrodes quickly in contact with a liquid environment and is also toxic to cells. In previous works, either changes in the backend process were done, replacing the aluminium by the much more inert platinum, or very thick layers of silicon nitride were deposited to passivate the chip satisfactorily [4][5][6]. So far, the different approaches require either a complex post-process after the CMOS fabrication [4,5] or complete changes in the backend process before finishing the CMOS process [3,7]. In the case when floatinggate field-effect transistors (FG FETs) are used [3,[8][9][10][11], the passivation layer can also serve as signal input dielectric layer. We have previously shown that the extracellular signal shapes of action potentials recorded with these devices are comparable to signal shapes usually recorded with open-gate FETs [9]. For FG FETs it is additionally demanded that the dielectric layer is thin, has a high interface capacitance, a low leakage current when immersed into an electrolyte solution and that it is biocompatible. Further, for the passivation process of aluminium, a deposition method with a low process temperature (<400 °C) is required. In this article we present a novel passivation method for FG FETs fabricated in a CMOS process, where an atomic layer deposited (ALD) thin film with a high dielectric constant serves as the only passivation material.To mimic the situation of passivating the top aluminium metal layer from a CMOS chip, we fabricated a set of test substrates. We used a p-doped silicon wafer (4″ silicon 〈100〉, resistivity 0.01-0.02 Ω cm (boron), thickness 525 µm) and e-beam evaporated 100 nm and 400 nm of pure aluminium on the front-and backside, respectively. We used a thin layer for the front side aluminium, because Sensors, which are designed and fabricated in complementary metal oxide semiconductor (CMOS) technology, have become increasingly important in the field of bioelectronics. The standardized industry processes enable a fast, cheap, and reliable fabrication of biosensor devices with integrated addressing and processing units. However, the interfacing of such chips with a liquid environment has been a challenge in recent years. Especially for interfacing living cells with CMOS biosensors different elaborate post-processes have been proposed. In this article we describe a novel and single step passivation of a CMOS biosensor using a bio-compatible high-permittivity thin film, which can be directly applied to the top aluminium layer of a CMOS process. The aluminium oxide and hafnium oxide multi-layer thin films were prepared using atomic layer deposition at low process temperature...

The growth behavior and step coverage of TiO 2 thin films deposited by liquid-delivery metallorganic chemical vapor deposition ͑MOCVD͒ at temperatures ranging from 410 to 490°C were investigated. The film growth rates were controlled by the gas phase thermal decomposition reaction of the precursors, and the reaction shows an apparent activation energy of ϳ90 kJ/mol. The gas phase thermal decomposition produced several intermediate precursor molecules with different sticking coefficients. The intermediate precursors played a crucial role in the film growth and step coverage change. As the growth rate decreases, the step coverage degrades, which can be explained by Langmuir's isothermal adsorption model of the precursors with the assumption of the various intermediate molecular structures of the precursors. The bulkier intermediate molecular structure of the precursor increases the steric hindrance between the previously adsorbed molecules and the impinging molecules so that the step coverage improves. The unusual step coverage of an MOCVD SrTiO 3 film previously observed for a low precursor injection rate was successfully explained using the results derived from the TiO 2 MOCVD and nonsticking property of the Ti-precursor molecules on the SrO surface.The ceramic thin films ͑Ba,Sr͒TiO 3 ͑BST͒, 1-4 SrTiO 3 ͑STO͒, 5 and Pb͑Zr,Ti͒O 3 6-8 deposited by metallorganic chemical vapor deposition ͑MOCVD͒ have been investigated by many researchers as capacitor materials of dynamic random access memories or ferroelectric random access memories. Considering the shrinking cell area of memory devices, these materials should be deposited on three-dimensional ͑3D͒ structures as contact holes. 9,10 The MOCVD method can produce these films with satisfactory growth rate, electrical properties, and conformal deposition over the severe 3D structures applicable to mass production. However, a nonuniform cation composition of the deposited film over a 3D contact hole has been reported even with the MOCVD technique when the contact hole diameter is below 150 nm. 11 In some cases, the films grew predominantly at the bottom corner of the contact hole, which is unusual. 11 To improve the thickness and composition uniformity of the multication oxide films, an understanding of the deposition behavior of the films on contact holes is necessary. However, it is not easy to understand the details of MOCVD of multicomponent oxide thin films because the deposition is affected by many complex factors. The above-mentioned materials commonly have a Ti component. Therefore, the MOCVD behavior and step coverage of the TiO 2 films are investigated first in this study. From these experimental results, the experimental results on the compositionally nonconformal STO thin film deposition that were previously reported by the authors are analyzed again in this paper. Figure 1 shows the schematic diagram of the system for the deposition of TiO 2 thin films. It is composed of an inverted vertical MOCVD reactor, where the sample surface faces downward, and a liquid...

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