Single Photolithography Process Research Articles

A novel capacitively coupled contactless conductivity detection (C4D) microfluidic chip integrated 3D microelectrodes for on-site determination of soil nutrients

Soil macronutrient nutrients (N, P and K) are critical for crop growth and agricultural production. The rapid and quantitative determination of soil nutrient content is of great importance to guide precise fertilization. To address the difficulty of synchronizing the detection of soil N, P and K with high sensitivity, this paper proposes a novel C4D microfluidic device with integrated 3D microelectrodes, which achieves lower detection limits for nutrients detection. The chip consisted of a crossover-type electrophoretic microchannels system and a 3D microelectrodes C4D system. 3D microelectrodes were constructed through clever design with only a single photolithography process required. The proposed microfluidic chips were used to detect potassium, ammonium, nitrate, and phosphate, with experimental results of standard solutions showing low detection limits of 5.24 × 10−5 g/L, 2.81 × 10−5 g/L, 2.35 × 10−5 g/L and 2.38 × 10−5 g/L. The microfluidic chips showed good reproducibility with relative standard deviations of less than 5 %. Separation experiments were also performed on soil samples with a resolution of K+ and NH4+ greater than 1.1. Accuracy was evaluated by adding 10 mg/L and 50 mg/L standards to the soil samples and results showed that recoveries were maintained at 80–120 %. The microfluidic chip with integrated 3D microelectrodes proposed in this work would effectively address the need for on-site, rapid detection of soil nutrients.

Fabrication and evaluation of suspended Micro‐heater using TiN

AbstractIn this study, suspended micro‐heater using TiN for decreasing power dissipation was fabricated and evaluated. The self‐supporting film of the suspended filament was developed by the low compressive stress SiO2 film deposited by the dc reactive sputtering method with rf substrate bias and the post annealing at 900°C. In the suspended structure process, single photolithography process and two wet etching process of HF and KOH solution were used. The power dissipation of the suspended heaters was obtained about 70 mW and it is indicated that the power dissipation is able to reduce than the other structure in previous research. Then, it is expected that the TiN micro‐heater using suspended structure is applicable to several MEMS sensors.

Three-dimensional long-period waveguide gratings for mode-division-multiplexing applications.

We propose a three-dimensional (3D) long-period grating structure that has a controllable grating width and depth and can be formed at any chosen position on the surface of a waveguide core with a single photolithography process. The process relies on the partial etching of small structures on the surface of a polymer waveguide through a waveguide mask with narrow apertures that define the grating pattern. The 3D grating structure allows the design of mode converters for any nondegenerate guided modes of a waveguide, regardless of their symmetry properties, and thus relaxes the design constraint of conventional two-dimensional waveguide gratings. To show the flexibility of the 3D grating structure, we present several mode converters fabricated with this structure. The mode-conversion efficiencies achieved are higher than 90% at the resonance wavelengths. In addition, we demonstrate a three-mode multiplexer by integrating a grating-based mode converter with two asymmetric directional couplers. The proposed grating structure together with the fabrication process can greatly facilitate the development of grating-based devices, especially for MDM applications.

Static Zero-Power-Consumption Coplanar Waveguide Embedded DC-to-RF Metal-Contact MEMS Switches in Two-Port and Three-Port Configuration

This paper reports on novel electrostatically actuated dc-to-RF metal-contact microelectromechanical systems (MEMS) switches, featuring a minimum transmission line discontinuity since the whole switch mechanism is completely embedded inside the signal line of a low-loss 3-D micromachined coplanar waveguide. Furthermore, the switches are based on a multistable interlocking mechanism resulting in static zero-power consumption, i.e., both the onstate and the offstate are maintained without applying external actuation energy. Additionally, the switches provide with active opening capability, potentially improving the switch reliability, and enabling the usage of soft low-resistivity contact materials. Both two-port single-pole-single-throw (SPST) switches featuring mechanical bistability and three-port single-pole-double-throw (SPDT) T-junction switches with four mechanically stable states are presented. The switches, together with the transmission lines, are fabricated in a single photolithography process. The loss created by the discontinuity of the switch mechanism alone is 0.08 dB at 20 GHz. Including a 500 m long transmission line with less than 0.4 dB/mm loss up to 20 GHz, the total insertion loss of the two-port devices is 0.15 and 0.3 dB at 2 and 20 GHz, and the isolation is 45 and 25 dB at 2 and 20 GHz. The three-port switches, including their T-junction transmission line, have an insertion loss of 0.31 and 0.68 dB, and an isolation of 43 and 22 dB, at 1 and 10 GHz, respectively. Actuation voltages are 23-39 V for the two-port switches and 39-89 V for the three-port switches. The microwave propagation in the micromachined transmission line and the influence of the different switch designs were analyzed by finite-element method (FEM) simulations of electromagnetic energy and volume current distributions, proving the design advantages of the proposed concept.

A high-temperature MEMS heater using suspended silicon structures

A high-temperature MEMS heater using suspended serpentine silicon beams as a filament is proposed for an infrared light source. The MEMS heater utilizes suspended silicon beams for thermal isolation and the mechanical support of heat resistors, and Pt/Ti layers for a Joule heating resistor deposited onto suspended silicon beams. An SiO2 insulator layer was deposited to provide electrical isolation between the thermal resistor and the silicon substrate. The proposed MEMS heater did not require a closed membrane-based back-cavity structure for thermal isolation. The heater is capable of being simply fabricated by a single photolithography process and subsequent silicon anisotropic etching and metal deposition processes. The fabrication process and driving characteristics of the MEMS heater are described. High temperature achieved by the heater was measured by IR camera image processing.

Pretilt Control of a Nematic Liquid Crystal on a Selectively Patterned Homeotropic Layer Over a Homogeneous Layer

We demonstrated the precise control of the pretilt of a nematic liquid crystal (NLC) on a selectively patterned homeotropic layer over a homogeneous alignment layer through a single photolithography process. Depending on the surface modulation parameters such as the periodicity and the relative dimension between two different patterns, the inhomogeneous substrate with periodic homeotropic and homogeneous patterns produces the pretilt angle of the NLC from zero to several tens degrees. Two different, homogeneous and homeotropic aligning forces for the NLC at the substrate are transferred into the bulk from the surface and result in an intermediate state of the pretilt depending on the surface modulation parameters.

An Si concentrator cell by single photolithography process

A mid-range concentrator cell by low-cost process is investigated and a new design is proposed. We tried to develop a single lithography CZ-Si cell process. The current conversion efficiency (not optimized) is 16% under X20 concentration without AR coating. The present moderate efficiency is possibly due to low bulk lifetime (approx. 5 μs after process). Cell efficiency and open-circuit voltage ( V oc) are expected to improve by using a better quality Si material and developing a low-stress process to maintain crystal quality. The equivalent circuit analysis reveals degradation of diode characteristics under concentration, which implies decline of fill-factor (FF) by use of low-quality concentrator optics.