The integration of embedded non-volatile memory (eNVM) devices in a Si CMOS manufacturing process requires to identify cost-effective process flow strategies and Si CMOS compatible materials. Hafnium dioxide (HfO2) is a promising dielectric for future Resistive Random-Access Memory (RRAM) applications. Following the "More than Moore" (MtM) approach, the advantage is given by the fact that the back-end-of-line (BEOL) integration of HfO2-based metal-insulator-metal (MIM) memory cells allows a cost-effective realization of embedded RRAMs. However, it still remains difficult in HfO2-based RRAM to further reduce energy dissipation and in addition to increase reliability for system-on-chip (SoC) applications. Hence, a detailed understanding of the atomic-scale mechanism and the identification of the material changes within the insulator are necessary. To address this issue, RRAM integration aspects were accompanied by fundamental materials research studies. First, non-destructive and in-operando Hard X-ray Photoelectron Spectroscopy (HAXPES) was performed to correlate the resistive switching effect with materials modifications at the Ti/HfO2 interface. The fundamental materials research insights were then transferred to integrated 1T1R devices in 4 kbit RRAM test arrays.

We have investigated the resistive switching behavior in stoichiometric HfO2 and oxygen-deficient HfO2−x thin films grown on TiN electrodes using reactive molecular beam epitaxy. Oxygen defect states were controlled by the flow of oxygen radicals during thin film growth. Hard X-ray photoelectron spectroscopy confirmed the presence of sub-stoichiometric hafnium oxide and defect states near the Fermi level. The oxygen deficient HfO2−x thin films show bipolar switching with an electroforming occurring at low voltages and low operating currents, paving the way for almost forming-free devices for low-power applications.

The electrical characteristics of different resistance states (virgin, OFF and ON) of a Ti/HfO2/TiN metal-insulator-metal device for resistance random access memory are investigated under different gas ambient. The influence of the atmosphere, the total pressure and the oxygen concentration during electrical measurements is underlined thanks to retention (I-t) and impedance spectroscopy (Z-f) measurements. The total pressure influences the current levels of the three different resistive states: when the total pressure decreases, the current increases, probably due to an increase of the concentration of oxygen vacancies in the HfO2.

This work reports the bipolar resistive switching behavior of more than 100 back-end-of-line (BEOL) integrated 600×600nm2 TiN/HfO2/Ti/TiN MIM devices in a 4 kbit memory array. Reliable current-voltage switching characteristics were only observed for devices with a thickness ratio of 1 (10 nm HfO2/10nm Ti), indicating the importance of the interface chemistry of the Ti/HfO2 interface. Moreover, the devices show good inter-cell uniformity and thus demonstrate promising prospects for embedded non-volatile memory (eNVM) applications.

The chemical and electronic modifications induced by the electroforming process on the Ti/HfO2/TiN-based resistive switching devices were investigated by non-destructive hard x-ray photoelectron spectroscopy (HAXPES). The results indicate an increase of the titanium top electrode oxidation at the interface with HfO2 after the electroforming process. Additionally, the binding energy values of the HAXPES peaks of the electroformed sample increased as compared to the as-prepared sample. The observed changes between both samples are attributed to the creation of n-type defects, such as oxygen vacancies, in the HfO2 layer near the Ti interface during the electroforming process.

This paper deals with the impact of the top metal electrode on the resistive switching properties of HfO2-based Metal-Insulator-Metal diodes. By screening five different metals as top electrode, Al–Cu–Hf–Pt–Ti, we have demonstrated the feasibility of the resistive switching effect on HfO2. Metals with a low enthalpy of formation of oxides ΔHf0 (Pt and Cu) lead to uni-polar switching whereas easily oxidizable metals with a higher ΔHf0 (Al, Hf and Ti) lead to bipolar switching. Cu-, Hf- and Pt-based devices show a degradation of the top electrode after the forming step by the formation of bubbles whereas such phenomenon was not observed in Al- and Ti-based devices. 200 switching cycles were performed on each device in order to extract the main parameters of the resistive switching effect: ION and IOFF currents in the mA range, ROFF/RON resistance ratio up to 5, Vset and Vreset, voltage levels around 1V, and powers dissipated during read and write operations in the μW and mW range, respectively. For all systems, the reset process dissipates higher power than the set process. From these results, the Ti top adlayer shows the best performance in terms of stability and resistive switching characteristics.

The Ti/HfO 2 /TiN-based system is a very promising candidate for Resistance change Random Access Memory (RRAM). By combining material science studies and integration in a Si CMOS technology, we succeeded to give quantitative insight in the resistive switching mechanism and to process a 4 kbit array with 1T1R RRAM devices. In particular, in-operando hard X-ray photoelectron spectroscopy allows to describe the resistive switching mechanism by a push-pull model of oxygen vacancies as a function of voltage polarity. Moreover, the characterization of integrated 600×600 nm2 TiN/Ti/HfO 2 /TiN 1T1R devices in the pulse-induced mode and the recent realization of a 4 kbit memory array have demonstrated promising performance for embedded non-volatile memory applications.

The authors demonstrate bipolar resistive switching in TiN/HfO2/Ti(top)/TiN devices using a (Bi) complementary metal-oxide semiconductor (CMOS) compatible technology process. The device performance includes a cycling endurance in dc sweeping mode >103. The results suggest that HfO2-based metal-insulator-metal devices with Si CMOS compatible metal electrodes may be well suited for future embedded nonvolatile memory applications. However, hysteretic current-voltage characteristics were only observed for a Ti top adlayer, whereas a Ti bottom adlayer integration did not show any resistive switching effect. Using x-ray photoelectron spectroscopy, the authors examined the interface chemistry of the Ti/HfO2 interface. It is clearly observed that Ti top adlayer deposition results in an increased nitrogen- and oxygen-gettering activity in contrast to Ti bottom adlayer. It follows that the formation of a nonstoichiometric HfO2 layer at the Ti/HfO2 interface is crucial for resistive switching.

This work addresses a 1T1R RRAM architecture, which allows for the precise and reliable control of the forming/set current by using an access transistor. The 1T1R devices were fabricated in a modified 0.25μm CMOS technology. The memory cells show stable resistive switching in dc as well as pulse-induced mode with an endurance of 103 and 102cycles, respectively. The variation of pulse widths as a function of amplitudes in 1R devices confirmed the set process distribution over a wide range of pulse widths (300ns–100μA), whereas the reset process variation is confined (1–3μs).

The integration of various functionality to (Bi)CMOS circuits is in the focus of the "More than Moore" approach. Here, we demonstrate the incorporation of surface acoustic wave (SAW) devices as well as of nonvolatile memories (NVM) into the Back end of line (BEOL) of Bi(CMOS) circuits. The added functionalities open new technological possibilities for high value microelectronics systems.

Laminated tooling consists of an array of stacked laminations that are mechanically clamped or bonded together, depending on the requirements of the manufacturing process. Various manufacturing processes that can benefit from tooling constructed of laminations include sheet metal forming, thermoforming, composites molding, metal extrusion, injection molding, resin transfer molding, and compression molding. When bonding of the laminations is required (e.g., incorporation of conformal cooling passages for injection molding temperature control) then laminations can be joined together by diffusion bonding, brazing and using adhesives. However, for a tooling engineer to effectively design a laminated tool, the physical and mechanical properties of these joints must be known. Consequently, a set of experiments is outlined for determining the tensile, shear, and peel strengths, tensile and shear elastic moduli, thermal contact resistance, and specific permeability (for gasses or liquids) of the aforementioned bonded joints for both steel and aluminum laminations. Some preliminary results with aluminum and future work are presented.

An investigation of the effects of system non-linearities, such as Coulomb friction and backlash, and undesirable structural dynamics, such as joint compliance, on the dynamic modeling and control of mechanical positioning systems is presented. These effects are often neglected in dynamic system analysis and control studies. An innovative, computer-controlled, mechanical positioning test bed was designedand constructed to facilitate investigations of these effects. The test bed allows fully adjustable, quantified and well-defined measurements of Coulomb friction, backlash, joint compliance and inertia. System identification and parameter estimation techniques are used to estimate and verify linear system parameters. Open-loop and closed-loop simulations of the system, incorporating the undesirable effects which can be exhibited by the test bed, are presented and compared with experimental results. The positioning performance of the servomechanism is shown to degrade with increases in Coulomb friction, backlash and joint compliance. Candidate control strategies to compensate for the above-mentioned adverse phenomena are described and their effectiveness is evaluated. Future experimental and theoretical work is described.

This work reports the bipolar resistive switching behavior of more than 100 back-end-of-line (BEOL) integrated 600×600nm2 TiN/HfO2/Ti/TiN MIM devices in a 4 kbit memory array. Reliable current-voltage switching characteristics were only observed for devices with a thickness ratio of 1 (10 nm HfO2/10nm Ti), indicating the importance of the interface chemistry of the Ti/HfO2 interface. Moreover, the devices show good inter-cell uniformity and thus demonstrate promising prospects for embedded non-volatile memory (eNVM) applications.