| People recognize gradually that indoor air pollution is sometimes morehazardous to human health than outdoor, how to take safety precautionary measuresto avoid the accident has become the safety issues of great concern to the state andsociety. Currently, there are some indoor air pollution detection methods, amongwhich sensor dectection method has the advantages of easy to use, direct readingwithout operation in addition to maintenance and correction, without professionaloperation, suitable for online testing. However, with the development of internet ofthings technology, traditional sensors can not meet the needs of the system becauseof lack of integration and embedding function, the height integration andcompatibility of the MEMS sensor bring hope to solve this problem.Si-based chip becomes a research hotspot of MEMS sensors, now the most ofSi-based MEMS sensors are pressure sensor, acceleration sensor, displacementsensor and other physical quantity sensors. And the successful chemical quantitysensors are few, because the smooth surface of the silicon and the poor affinitybetween silicon and sensitive material cause low adhesion binding property ofsensitive material, which affects the stability and reliability of the sensor. Therefore,it is necessary to research the silicon-based chip and micromachining technologysuitable for the chemical quantity sensor to detect toxic gas.In this paper, aiming at the problems of the smooth surface of the silicon and thepoor affinity between silicon and sensitive material, new silicon-based micro-structure sensor with nanoporous alumina membranes as the middle layer ispresented, and is verified the rationality of the structure by ANSYS finite elementsimulation method; the anodizing process of aluminum-based is carried out, and the nanoporous alumina membranes is migrated to the silicon surface; polyaniline andmetal oxides as the source material, polyaniline/inorganic composite materials aresynthesized through in-situ chemical polymerization method and characterized byphysicochemical analytical tools; MEMS gas sensor is made through micro-processing technology, thin film technology, electrochemical anodic oxidationprocess, sol-gel technology and welding technology, and the performance is testedand analyzed for benzene vapor, ammonia gas and formaldehyde gas respectively,and its sensitive mechanism is discussed. The main content was as follows:1. A new silicon-based micro-structure chip is designed. Nanoporous aluminumoxide layer is introduced in the silicon-based microstructure, and the poroushoneycomb structure of the surface increases the adhesion between the substrate andthe sensitive material. According to the different positions of micro-heater, signalelectrode and nanoporous alumina layer, four programs are designed, the concretestructure and sizes of the micro hot plate is designed based on the designrequirements, and the temperature distribution of the four micro-structures issimulated through ANSYS finite element method, and the best solution is electedaccording to the complexity of the structure and the simulation results.2. Polyaniline/inorganic composite sensitive materials are synthesized and theproperties are studied. Polymer/inorganic composite materials can work at lowtemperature, and both can play the features of polymer sensing materials withappropriate modification, modification, design and synthesis for detecting objects,and can integrate gas-sensitive response characteristics of inorganic materials, whichcan improve the selectivity, the sensitivity and stability of the sensor. The synthesisand modification process of PANI/inorganic composite sensitive materials arestudied, and composite sensitive materials are characterized by scanning electronmicroscopy, UV-visible spectroscopy and differential thermal analysis methods todetermine the validity of its process and the basic characteristics and the finalproduct.3. The aluminum-based anodizing process and a growth method of organicsemiconductor in mesopores are studied. The aluminum film is prepared on thesilicon substrate by magnetron sputtering and vacuum evaporation method, and madeinto nanoporous alumina membranes by electrochemical anodic oxidation method;the aluminum film preparative techniques, the effect of electrochemical polishing, the type and concentration of electrolyte and formation methods of aluminum on thenanoporous alumina membranes, and the formation mechanism of nanoporousalumina membranes are studied; the sensitive material film are formed on the surfaceof nanoporous alumina membranes through sol-gel method, and the formationmechanism is explored.4. The silicon-based micro-structure sensor is prepared and tested. Micro heateris made of Fe/Cr/Al-Ni/Cr alloy replacing Pt resistance, and its preparation processand heating characteristics are researched. A new Si-based stack micro-structure chipis prepared through semiconductor microfabrication technology, thin film technologyand electrochemical anodic oxidation technology. The sensor is detected for benzenevapor, ammonia gas and formaldehyde gas, its gas sensing characteristics is analyzed,and the gas sensing mechanism is discussed.The results of experiments show that: nanoporous alumina film has beensuccessfully transplanted on silicon substrate through anodic oxidation process of thealuminum film-based, the introduction of nanoporous alumina membranes into thesilicon-based micro-structure sensor increases the adhesion of the sensitive material,and polyaniline/inorganic sensitive materials synthesized have good sensitivity tobenzene vapor, ammonia gas and formaldehyde gas. |
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