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3D integration has well-developed for traditional CMOS technology operating at room temperature, but few studies have been performed for cryogenic applications such as quantum computers. In this paper, a wafer-to-wafer bonding of superconductive joints based on niobium nitride (NbN) is performed to demonstrate the possibility of 3D integration of superconducting chips. The NbN thin films are deposited by magnetron sputtering. Its high critical temperature (15.2 K) is achieved by optimizing the sputtering recipe in terms of N2 flow rate and discharge voltage. Wafer-level bumping is bonded by the thermo-compression method. The sheet resistance of the thin film and the contact resistance of the joints are measured by the Greek-cross (4-point Kelvin method) and daisy chain structures at cryogenic temperature, respectively. Direct-bonding wafers with NbN superconductive joints avoid using adhesive layers and the bonding interface could still present superconducting electrical connections in a cryogenic environment above 4 K, which will allow us to use a smaller and high-cooling power cryostat. The contribution of this work could lead to the fabrication of multi-layered superconducting chip that operates beneficially in cryogenic temperature, which is essential in building scalable quantum processors., Electronic Components, Technology and Materials, QID/Ishihara Lab, Quantum Circuit Architectures and Technology

Printing of electronics is pursued as a low-cost alternative to conventional manufacturing processes. In addition, owing to relatively low process temperatures, flexible substrates can be used enabling novel applications. Among flexible substrates, paper was found to be a particularly interesting candidate, since it has an order of magnitude lower price than low-cost polymer alternatives, and is biodegradable. As ink materials, organic and metal-oxide semiconductors are thoroughly being investigated; however, they lack in electric performance compared to silicon in terms of device mobility, reliability, and energy efficiency. In recent years, liquid precursors for silicon were found and used to create polycrystalline silicon (poly-Si). However, fabrication of transistors on top of low-cost flexible substrates such as paper has remained an outstanding challenge. Here we demonstrate both p-channel and n-channel poly-Si thin-film transistors (TFTs) fabricated directly on top of paper with field-effect mobilities of 6.2 and 2.0 cm2/V s, respectively. Many fabrication challenges have been overcome by limiting the maximum process temperature to approximately 100 °C, and avoiding liquid chemicals commonly used for etching and cleaning. Patterning of poly-Si has been achieved by additive selective crystallization of the precursor film using an excimer laser. This work serves as a proof of concept, and has the potential to further improve device performance. Owing to the low-cost, biodegradable nature of paper, and the high performance, reliability, and energy efficiency of poly-Si TFTs, this work opens a pathway toward truly low-cost, low-power, recyclable applications including smart packages, biodegradable health monitoring units, flexible displays, and disposable sensor nodes., QID/Ishihara Lab, (OLD)Quantum Integration Technology, EKL Processing

Printing of electronics has been gaining a lot of attention over the past decade as a low cost alternative to conventional electronic fabrication methods. A significant development in this area was the possibility to print a silicon precursor, polydihydrosilane, which can directly be transformed into polycrystalline silicon by an excimer laser treatment. Due to the limited laser heat diffusion, low-cost flexible substrates such as plastics and even paper could be used that typically have low thermal budgets. Since the silicon precursor is sensitive to ultraviolet light and may transform in a photochemical reaction, the question arises whether the excimer laser crystallization is predominantly photochemical or rather a thermal reaction. In this work, a model is developed and reflected to experimental data, to understand the physics behind the process. Through finite-element analysis and experimental characterizations it was observed that the physics behind the process was predominantly thermal, and that instead of an intermediate transition to a-Si, a direct transformation to poly-Si exists. By understanding this process, the treatment can be optimized or more efficient tools can be used that would enable a low cost production of high performing silicon devices, QID/Ishihara Lab, Tera-Hertz Sensing, (OLD)Quantum Integration Technology

Currently, research has been focusing on printing and laser crystallization of cyclosilanes, bringing to life polycrystalline silicon (poly-Si) thin-film transistors (TFTs) with outstanding properties. However, the synthesis of these Sibased inks is generally complex and expensive. Here, we prove that a polysilane ink, obtained as a byproduct of silicon gases and derivatives, can be used successfully for the synthesis of poly-Si by laser annealing, at room temperature, and for n- and p-channel TFTs. The devices, fabricated according to CMOS compatible processes at 350 °C, showed field effect mobilities up to 8 and 2 cm2/(V s) for n- and p-type TFTs, respectively. The presented method combines a low-cost coating technique with the usage of recycled material, opening a route to a convenient and sustainable production of large-area, flexible, and even disposable/single-use electronics., Tera-Hertz Sensing, QID/Ishihara Lab, QuTech, (OLD)Quantum Integration Technology

QID/Ishihara Lab

A method for low-temperature formation of a silicon/silicon-oxide structure on a substrate is described wherein the method comprises: forming a first (poly)silane layer over at least part of a substrate; transforming said first (poly)silane layer directly into a (crystalline) silicon layer by exposing said first (poly)silane layer to UV radiation comprising one or more wavelengths within the range between 100 and 450 nm; forming a second (poly)silane layer over at least part of said substrate; and, transforming said second (poly)silane layer directly into a silicon oxide layer by exposing said second (poly)silane layer to oxygen and/or ozone and to UV light comprising one or more wavelengths within the range between 100 and 450 nm., Quantum Engineering, Electrical Engineering, Mathematics and Computer Science

Printing electronics has led to application areas which were formerly impossible with conventional electronic processes. Solutions are used as inks on top of large areas at room temperatures, allowing the production of fully flexible circuitry. Commonly, research in these inks have focused on organic and metal-oxide ink materials due to their printability, while these materials lack in the electronic performance when compared to silicon electronics. Silicon electronics, on the other hand, has only recently found their way in solution processes. Printing of cyclopentasilane as the silicon ink has been conducted and devices with far superior electric performance have been made when compared to other ink materials. A thermal annealing step of this material, however, was necessary, which prevented its usage on inexpensive substrates with a limited thermal budget. In this work, we introduce a method that allows polycrystalline silicon (poly-Si) production directly from the same liquid silicon ink using excimer laser irradiation. In this way, poly-Si could be formed directly on top of paper even with a single laser pulse. Using this method, poly-Si transistors were created at a maximum temperature of only 150?°C. This method allows silicon device formation on inexpensive, temperature sensitive substrates such as polyethylene terephthalate, polyethylene naphthalate or paper, which leads to applications that require low-cost but high-speed electronics., Microelectronics, Electrical Engineering, Mathematics and Computer Science

Methods for manufacture of a submicron semiconductor structure on a substrate are described. The method may comprise: forming at least one template layer over a support substrate; forming one or more template structures, preferably one or more recesses and/or mesas, in said template layer, said one or more template structures comprising one or more edges extending into or out of the top surface of said template layer; coating at least part of said one or more template structures with a liquid semiconductor precursor, preferably a liquid silicon precursor; and, annealing and/or exposing said liquid semiconductor precursor coated template structures to light, wherein during said annealing and/or light exposure a part of said liquid semiconductor precursor accumulates by capillary forces against at least part of said one or more edges, said annealing and/or light exposure transforming said accumulated liquid semiconductor precursor into a submicron semiconductor structure extending along at least part of said one or more edges., Microelectronics, Electrical Engineering, Mathematics and Computer Science

Printing is attractive for manufacturing flexible circuits. This manuscript presents our investigation of single-grain Si TFTs fabricated from printed liquid-Si, on a polyimide substrate with the maximum process temperature of 350 °C. The field-effect mobility is 460 cm2/Vs for electrons and 121 cm2/Vs for the holes. CMOS inverters were also fabricated. The devices function at the bending diameter of 3 mm. The device performance under the bending stress was discussed., Microelectronics, Electrical Engineering, Mathematics and Computer Science

A method for forming a silicon layer using a liquid silane compound is described wherein said method comprises the steps of forming a first layer on a substrate, preferably a flexible substrate, said first layer comprising a (poly)silane; and, irradiating said first light ight comprising one or more wavelength within the range between 200 and 400 nm for transforming said polysilane in silicon, preferably amorphous silicon or polysilicon., Microelectronics, Electrical Engineering, Mathematics and Computer Science

We review our recent achievements in monolithic 3D-ICs and flexible electronics based on single-grain Si TFTs that are fabricated inside a single-grain with a low-temperature process. Based on pulsed-laser crystallization and submicron sized cavities made in the substrate, amorphous-Si precursor film was converted into poly-Si having grains that are formed on predetermined positions. Using the method called µ-Czochralski process and LPCVD a-Si precursor film, two layers of the SG Si TFT layers with the grains having a diameter of 6µm were vertically stacked with a maximum process temperature of 550°C. Mobility for electrons and holes were 600cm2/Vs and 200cm2/Vs, respectively. As a demonstration of monolithic 3D-ICs, the two SG-TFT layers were successfully implemented into CMOS inverter, 3D 6T-SRAM and single-grain lateral PIN photo-diode with in-pixel amplifier. The SG Si TFTs were applied to flexible electronics. In this case, the a-Si precursor was prepared by doctor-blade coating of liquid-Si based on pure cyclopentasilane (CPS) on a polyimide (PI) substrate with maximum process temperature of 350°C. The µ-Czochralski process provided location-controlled Si grains with a diameter of 3µm and mobilities of 460 and 121cm2/Vs for electrons and holes, respectively, were obtained. The devices on PI were transferred to a plastic foil which can operate with a bending diameter of 6mm. Those results indicate that the SG TFTs are attractive for their use in both monolithic 3D-ICs and flexible electronics., Microelectronics, Electrical Engineering, Mathematics and Computer Science

Solution process of silicon will provide high-speed transistor fabrication with low-cost by, for example, roll-to-roll process. In this paper, a low-temperature process (350?°C) is reported for fabrication of high-quality Si devices on a polyimide substrate from doctor-blade coated liquid-Si. With this method, different semiconductor devices have been fabricated, reporting a carrier mobility of 460 cm2/V s and 121 cm2/V s for electrons and holes, respectively. The devices were peeled off and transferred onto a polyethylene naphthalate foil to achieve flexible devices. CMOS inverters were also fabricated and show full output swing., Microelectronics, Electrical Engineering, Mathematics and Computer Science

Solution process of silicon using liquid-Si is attractive for fabrication of high-speed flexible electronics. We have fabricated single-grain Si TFTs on location-controlled Si grains with longpulse excimer laser crystallization of spin-coated liquid Si film. The maximum grain diameter is 3.5?m, and the mobilities for electrons and holes are 423cm2/Vs and 118cm2/Vs, respectively., Microelectronics, Electrical Engineering, Mathematics and Computer Science

Microelectronics, Electrical Engineering, Mathematics and Computer Science

Liquid silicon is found as the material combining both the advantages of high quality silicon devices and the low cost solution processing method. Single-Grain Thin-Film Transistors can be produced by Excimer Laser Annealing of the resulting film and grain location control by the µ-Czochralski process. Other works have used spin-coating and inkjet printing for liquid silicon based devices, however both processes are not roll-to-roll process compatible. In addition a high thermal annealing step (650°C), incompatible to plastics, is required for the reduction of hydrogen content before laser crystallization. In this work, both issues are focused on. A precursor of the gravure printing process, doctor blade coating, is used to imitate a roll-to-roll compatible solution process and is optimized to produce uniform films of liquid silicon. Excimer Laser Annealing is used as a low temperature pre-annealing method to decrease the hydrogen content for crystallization. Pure cyclopentasilane has been used as the liquid silicon material. Silicon dioxide surface modification by 0.55%HF dip results in a better wetting of the liquid together with an elevated temperature of 70°C. Higher temperatures lead to even better wetting properties, but more liquid silicon will evaporate. After UV polymerization of the CPS for 20 minutes and thermal annealing at 350°C for 1 hour, an a-Si layer has been formed. Excimer Laser pre-annealing of many low energy shots removes hydrogen without significant deterioration of the film. A maximum grain size of 5µm has been produced by using a long pulse configured laser recipe that decreases the number of shots linearly while increasing the laser energy density by 50mJ/cm². SG-TFTs on polyimide have been manufactured at the maximum processing temperature of 350°C. The mobility of the NMOS was ..., and the mobility of the PMOS was .... [to be obtained by mid June]. Finally, a next step towards gravure printing has been taken, by advancing the doctor blade, Electronic Components, Technology and Materials, Microelectronics & Computer Engineering, Electrical Engineering, Mathematics and Computer Science

With the so many available sorts of E-paper, the optimal performing and consumer friendly E-paper needs to be found in order to win the E-paper market. As result of this, researchers from the TU Delft are currently developing a technology that can replace all ordinary papers by one single device, which has outperforming characteristics compared to the current E-papers: Super E-paper. In order to launch this superior product, a research needs to be conducted with regards to the optimum driving method of the Super E-paper. This thesis shall not only investigate what the optimum driving method of the Super E-paper is, by applying different types of power to the product. But also describe our steps towards this measurement by sharing background knowledge, linking theory to practice, designing the source that will be used for our Super E-paper measurements. For the measurements, several variables are analysed: · Voltage amplitude · Frequency of the source · Duty cycle of the source, Microelectronics, Microelectronics & Computer Engineering, Electrical Engineering, Mathematics and Computer Science