In this paper, a systematic method for designing a basic thermal MEMS design is discussed using the example of a thermal micromechanical mirror developed by MIET. The mirror is made with microelectronic technology and consists of two movable bimorph structures made of aluminum and silicon dioxide. A reflective element with an aluminumcoated surface is attached to the movable beams. The movable beams are fixed to a silicon substrate and are controlled by applying а voltage to electrical heating elements formed inside the movable beams. Heating causes uneven expansion of the materials that make up the beams, which in turn causes the structure to move. The proposed design process involves algorithmic design using three developed models to determine the initial parameters of the thermal actuator, its static and dynamic characteristics, and the response to the control action. The use of such an algorithm in the design flow allows for a quick selection of the basic geometric and physical parameters that should ensure that the actuator has the required performance and characteristics. This significantly reduces the time taken during the initial design phase of the device.
This paper presents the results of gas-phase deposition of silicon epitaxial layers studies obtained under real production conditions. The research is based on innovative techniques that have expanded the physical understanding of the process, which has improved the adequacy of the final results. Based on the developed physical modeling methodology, a study of the silicon epitaxial layers deposition process was carried out. The results were processed in a generalized form and could be represented by simple criterion relations. Based on the studies the area of the technological process with maximum possible homogeneity of silicon epitaxial layers deposition parameters was determined. It was shown that the silicon epitaxial layers deposition rate is determined by the interaction between the outgoing flow (from the nozzle) and reverse flow (at the moment when the wafer is between the nozzles). The use of the technique based on the autodopping effect showed that the distribution of the dopant impurity (from the local source) in the deposition zone is inhomogeneous and a significant part of the impurity is transferred in the direction of the jet flow. The plasma chemical deposition process of SiHxNy has been studied. As a defining parameter of the plasma chemical deposition process, the number ReL characterizing the gas dynamics of the process is chosen. Studies were performed at pressures in the reaction chamber of 100, 50, and 10 Pa, which corresponds to values ReL =1.2, 0.8, and 0.4. It is shown that greater uniformity of the deposited layer occurs at higher pressures.
KEYWORDS: Deposition processes, Chemical vapor deposition, Microelectromechanical systems, Low pressure chemical vapor deposition, Visualization, Process modeling, Chemical analysis, Analog electronics, Doping, Visual process modeling
This paper considers methods and means of experimental investigation of gas-phase deposition of layers of different materials realized in CVD and LPCVD technologies. The need to obtain layers of a given composition and parameters requires careful studies of the physical and chemical laws of such processes. As shown by the analysis of literary sources, most of the available works on these topics are performed on the basis of various computer software tools and results and conclusions represent a large set of particular cases, since a particular design of the reactor with specific geometric parameters is being investigated. In our opinion, the creation of analytical models of gas-phase deposition processes is an important component of a comprehensive study of gas-phase processes and for such purpose in this paper we present a methodological basis for the studies of CVD and LPCVD processes: a technique for visualizing the interaction of the ASG flow with the deposition surface (substrates), a technique based on the effect of self-doping and methods of physical and analog modeling.
This paper considers the multi-sectional structure of the thermal micromechanical mirror element, developed and manufactured by the National Research University "MIET". The structure consists of a movable part and a fixed part. The movable part includes a pair of thermal microactuators based on a multilayer structure of silicon oxide and aluminum, and a mirror reflecting element coated with aluminum. The fixed part is the area of attachment of the element to the silicon wafer. The temperature distribution along the length of the multi-sectional structure of the thermal microactuator is calculated taking into account the effect of the system of transverse heat-conducting structures under various heating conditions. An essential difference between the calculations, reaching two times, was established. The experimental studies showed the adequacy of the calculation results and proved that the calculation of the temperature distribution should take into account the cooling effect of transverse heat-conducting structures. Based on the calculations and experimental studies, a technique is proposed for analyzing the thermal state of the microactuator that takes into account the cooling effect of the transverse heat-conducting structures.
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