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For the development of micro-electro-mechanical system (MEMS) technology during the past several years, MEMS design has requirements of high precision, high efficiency, iterative design, joint design of structure and circuit and so on. With the improvement of thermal wind sensor performance requirements and the complexity of the application environment, it is becoming increasingly difficult to ignore the impact of environmental factors. However, there is no system-level model considering the influence of environmental factors adequately in macro model. To solve these problems, a 2D thermal wind sensor macro model considering environmental factors is proposed. In order to build a macro model which can reflect the output of sensors in different environments, this paper, starting from the basic law of heat transfer, proposes an accurate macro model of the thermal wind sensor. The model proposed in this study accurately considers the influence of thermal and transport properties in different environments, and can be simulated together with the interface circuits in Cadence software. The results indicate that the variation of temperature and atmospheric pressure in the natural range can affect the sensor output by more than 15%, and the influence of relative humidity should not be ignored when the temperature is higher than 70 °C. Furthermore, the flow direction over the sensor can be further studied according to the 2D equivalent circuit model. The simulation results agree well with the experimental results, and the results can provide a valuable reference for the research and practical application of thermal wind sensors.

In this paper, the simple, rejection-based kinetic Monte Carlo simulation method is applied for the approximate simulation of the etch rates and three-dimensional etch structures during anisotropic wet etching of sapphire. Based on the analysis of the composition of the atomic structure of sapphire, a model of the simplified atomic structure of sapphire is proposed, which reduces the difficulty of classifying types of surface atoms on the different crystallographic planes. This enables adopting a previously proposed six-index classification method (to differentiate effectively between the various surface atoms of sapphire) and a previously proposed removal probability function (RPF) (to link the removal probability of the surface atom with the configuration of its neighbors). By reducing errors between simulated rates and experimental rates of 11 typical crystallographic planes in the and crystallographic zones continuously with an evolutionary algorithm, reasonable values of nine energy parameters of the RPF are obtained. The simulated results describe approximately the experimental counterparts.

In this paper, we propose a thermal wind speed sensor Verilog-A model with thermal-fluid-electric hybrid characteristics. Because the structure of the thermal wind sensor and the interface circuit chip are designed separately, which cannot effectively carry out MEMS-IC (integrated circuit) co-simulation, the overall performance of the sensor and interface circuit chip is prone to large deviation. At the same time, the separation of MEMS structure and IC design process leads to long product development cycle and high cost. This paper proposes an improved simulation model by analyzing the behavior characteristics of the thermal wind speed sensor. The simulation model consists of 11 thermistors, 3 capacitors, a voltage-controlled voltage source, and a voltage-controlled current source. The Taylor series expansion of the differential equation of heat conduction is carried out, and then the thermistor and capacitor networks are established according to the corresponding relationship between the thermal parameters and the electrical parameters, including the thermal conduction unit, the convection unit and the heat capacity in the chip. The model fully considers the effects of various physical effects and parasitic effects, and is implemented using the hardware description language Verilog-A. The sensor and interface circuit can be simulated simultaneously to optimize the circuit design. It is beneficial to the integration of sensors and interface circuit, reducing the number of tape-outs, increasing the success rate, and reducing costs. The consistency between the simulation results and the experimental curves verified the correctness of the macro model. The behavior characteristics of constant power (CP) and constant temperature heating were described. In CP mode, the output voltage error is less than ± 6.5%, the chip temperature error is less than 4.0%. The presented modeling approach can be the basis for the development of complete MEMS-IC design technology library of thermal wind speed sensor, aiming at optimum designs of integrated thermal wind speed sensor.

The two-dimensional (2D) dynamic cellular automata (CA) method for photoresist etching simulation has been successfully improved by using novel update rules and a novel compensation value calculation method. The improved 2D dynamic CA method demonstrates to be more efficient and accurate. The deep ultraviolet (UV) lithography processes of SU-8 photoresists have been successfully simulated using aerial image simulation, exposure simulation, post-exposure bake simulation and development simulation models, based on the improved CA method. Simulation results demonstrate good agreement with the experimental results. This is useful to optimize the UV lithography process of SU-8 photoresists and improve the efficiency of the design of some micro-electro-mechanical systems devices.

This paper presents a novel 3D continuous cellular automaton (CA) model with high index planes such as (2 1 1), (3 1 1), (3 3 1) and (4 1 1) efficiently incorporated. A dynamic algorithm has also been developed to speed up the simulation process and reduce the memory usage. A 3D silicon anisotropic etching simulator, SEAES, has been implemented based on the 3D continuous CA model and the dynamic algorithm. The simulation results by SEAES have been found to be in good agreement with the experimental results, and the arbitrarily complex mask shapes and the merging of 3D etching profiles can be both efficiently and accurately handled. This is identified to be useful for the research of anisotropic etching technologies and the development of micro-electro-mechanical systems (MEMS) design.

This paper presents a two-dimensional (2D) modified cellular automata (CA) algorithm for accurate boundary movement of deposition process simulation. The algorithm incorporates deposition rate calculation methods based on a cell structure. Isotropic and anisotropic deposition processes were successfully simulated by the algorithm, and the simulation profiles show good agreement with available experimental results. The deposition process with defects on the substrate was also implemented using this algorithm. The 2D modified CA algorithm demonstrates accuracy and capability of handling complex boundary and initial conditions. It is useful for the deposition process simulation of microelectromechanical systems and integrated circuits.

A novel two-dimensional (2D) dynamic cellular automata (CA) model is presented for photoresist etching process simulation. The speed of the dynamic CA model increases by over ten times compared with the 2D static CA model. At the same time, the simulation accuracy is also increased in this model. The dynamic CA model has been successfully tested using some well-known etch-rate distribution test functions and is demonstrated to be stable even in areas where the fluctuation in etch rates is very sharp.

An online test structure for measuring the thermal expansion coefficient (TEC) of surface micromachined polysilicon beams is presented by using clamped–clamped beams. In this structure, the polysilicon beam is heated by applying direct current voltage between two anchors, causing it to expand. The thermal expansion of the beam is restricted due to the clamped–clamped boundary, while the pull-in voltage is measured by applying the other varying voltage between the beams and substrate. Based on the electrothermal properties of the test structure and the pull-in approach, an analytical model and an extracting method for the TEC are developed. Validation of the analytical model has been confirmed by FEM simulation and experiments. In the experiments, current–voltage measurements are only required, and all measurements can be carried out in free air. Measured average value of the TEC is (2.49 ± 0.03) × 10−6 K−1 with temperature ranging from 300 to 350 K.

Three-dimensional oblique microstructures of SU-8 negative thick photoresists have drawn more attention with the rapid development of inclined UV lithography technology. In this paper, a simple model based on the Fresnel diffraction theory is developed to simulate the inclined UV lithography and predict the profiles of developed oblique SU-8 structures by utilizing the paraxial approximation approach. The reflection, refraction, absorption of the SU-8 photoresists and the reflection at the wafer surface are integrally incorporated in the model to improve the accuracy. The parameters, which have significant influence on the profile quality, have been studied in simulation. Simulation results demonstrate good agreement with the experimental results, where the oblique SU-8 structures were fabricated on glass and silicon wafers. To eliminate reflected UV light at the wafer surface, Ti films were sputtered on the glass wafers, followed by wet oxidation, thus employed as an antireflection layer. By contrast, the silicon wafers were used to fabricate the oblique SU-8 structures with reflected induced patterns. This model is useful to optimize the inclined UV lithography process of SU-8 thick photoresists and improve the efficiency of the design of some micro-electro-mechanical system devices.