面向脑颅压检测的声表面波传感器设计及制作工艺研究
发布时间：2018-12-17 05:31
【摘要】：脑积水是一种在婴幼儿和老年人群中常见的疾病,其病因在于脑脊液分泌过多或(和)循环、吸收障碍引起颅内压的增高,因而导致头颅增大、头痛、智力障碍等。目前,脑积水治疗手段主要采用脑室腹腔分流术,通过在病人体内植入分流阀系统,将过多的脑脊液引流到腹腔中被吸收掉,从而使脑颅压保持在正常范围内;但该分流阀系统故障率较高,容易发生阻塞、过引流或者引流不足等问题,严重威胁病人的生命安全。目前,主要通过CT或MRI来辅助调整阀门大小,但该方法存在测量精度较差、成本较高且无法实现连续测量等缺点。针对以上不足,本文以基于声表面波原理的脑颅压传感器为研究对象,通过传感器理论建模和有限元仿真等手段,对传感器的温度补偿策略、结构设计方法及加工工艺等关键技术进行深入研究,实现对脑颅压的低成本连续测量功能。针对脑颅压传感器温度漂移问题,本文设计了基于ST切型石英基底的差分式脑颅压传感器结构。由于ST切型石英具有良好的温度稳定性,本文将其作为传感器的压电基底,通过在上表面蒸镀铝电构成叉指换能器和反射栅,设计了谐振器型结构。本文提出了一种将经验公式与耦合数学模型相结合的局部快速仿真传感器结构参数的方法,提高了传感器设计效率。首先,利用经验公式对传感器的结构参数进行初始设计,确定其主要取值范围。然后,通过建立传感器耦合数学模型,更精确地实现仿真设计。以传感器S散射参数幅值为目标,通过研究传感器的电极指条对数、膜厚比等参数变化规律并进行设计,得到了Q值较高的器件。最后,通过设计双谐振器型结构,对传感器进行差分补偿,改善了传感器的温度特性。对传感器进行了相关实验,测得精度约为3.21%,达到了本文所提出的设计目标。由于ST切型石英基底机电耦合系数较小,本文利用不同材料温度系数相反的特性,通过在128°YX切型Li Nb O3压电基底上蒸镀Si O2薄膜,设计了一种多层膜结构的新型传感器,它具有较大机电耦合系数和良好温度稳定性。首先,建立传感器有限元仿真模型,利用特征频率分析,计算声表面波在压电基底材料上的传播速度。分析了在不同Si O2薄膜厚度下,机电耦合系数的变化规律。其次,通过将温度场耦合到仿真模型中,计算不同温度下声表面波传播速度,研究了多层膜结构Si O2膜厚与温度系数变化规律。确定多层膜结构零温度系数对应的Si O2镀膜厚度及机电耦合系数大小。最后,通过频域仿真,得到了多层膜结构传感器的S参数,并对器件进行了静态实验测试和验证,该多层膜结构测得的机电耦合系数远大于石英晶体。通过研究MEMS加工工艺,制作了传感器样机。利用干法刻蚀工艺,在压电基底上制作叉指和反射栅电极结构。针对PECVD蒸镀较大厚度Si O2薄膜热应力问题,通过改进工艺流程,采用分时镀膜释放热应力的方法,解决了较大膜厚下Si O2表面出现破裂的问题。为了减小传感器尺寸并提高灵敏度,设计合金膜片式传力结构。但由于工艺达水平的局限性,导致该方法制作的传感器重复性一般。为了解决这一不足,研制了压电敏感元件直接受压的“三明治”式封装结构,有效地改善了传感器的重复性。搭建了传感器实验测试系统。采用0.01%精度的硅谐振传感器作为基准,通过Mensor压力控制器和恒温箱分别控制压力和温度输出,对传感器的压力和温度特性进行实验研究,验证了温度补偿方案的可行性。本文提出的声表面波脑颅压传感器,实现了基本压力参数的测量功能,解决了现有脑颅压测量精度不高或不能连续测量等问题,后续设计天线能够实现无源无线测量。通过设计传感器的量程,也可以将其扩展到心脏血压等其它生理参数的测量,本文的研究成果在临床应用方面具有潜在的重要价值。
[Abstract]:Hydrocephalus is a common disease in infants and the elderly, the cause of which is the excessive or (and) circulation of the cerebrospinal fluid, which causes an increase in the intracranial pressure, resulting in an increase in the head, a headache, an intellectual disorder, and the like. At present, the method for treating the hydrocephalus mainly adopts a ventriculoperitoneal shunt, and the through-flow valve system is implanted in the patient, the excessive cerebrospinal fluid is drained into the abdominal cavity to be absorbed, so that the cranial pressure is kept in a normal range, the fault rate of the shunt valve system is high, the blockage is easy to occur, the problems of over-drainage or underdrainage and the like are serious, and the life safety of the patients is seriously threatened. At present, the size of the valve is mainly assisted by CT or MRI, but the method has the disadvantages of poor measurement precision, high cost and no continuous measurement. In view of the above shortcomings, this paper makes an in-depth study on the temperature compensation strategy, structural design method and processing technology of the sensor by means of sensor theory modeling and finite element simulation, based on the theory of surface acoustic wave, as the research object. and the low-cost continuous measurement function of the brain intracranial pressure is realized. In order to solve the problem of the temperature drift of the brain-cranial pressure sensor, the structure of the differential type brain-cranial pressure sensor based on the ST-cut quartz substrate is designed. As the ST-cut quartz has good temperature stability, the piezoelectric substrate of the sensor is used as the piezoelectric substrate of the sensor, and the interdigital transducer and the reflecting grating are formed by vapor-plating on the upper surface, and the resonator type structure is designed. In this paper, a method of combining the empirical formula with the coupled mathematical model is proposed, and the design efficiency of the sensor is improved. First, using the empirical formula, the structural parameters of the sensor are initially designed and the main value range is determined. and then the simulation design is realized more accurately by establishing a sensor coupling mathematical model. With the sensor S scattering parameter amplitude as the target, the parameters of the parameters such as the logarithm of the electrode finger of the sensor and the thickness ratio of the film were studied and the design was carried out to obtain the device with higher Q value. Finally, by designing the double-resonator type structure, the differential compensation of the sensor is carried out, and the temperature characteristic of the sensor is improved. The relative experiment of the sensor is carried out, the accuracy of the measurement is about 3.21%, and the design goal set forth in this paper is achieved. Because the electromechanical coupling coefficient of the ST-cut type quartz substrate is small, a new type of sensor for multi-layer film structure is designed by vapor-plating the Si O2 thin film on a 128-degree YX-cut Li Nb O3 piezoelectric substrate by using the characteristics of the opposite of the temperature coefficient of different materials. It has a large electromechanical coupling coefficient and good temperature stability. First, a finite element simulation model of the sensor is established, and the propagation velocity of the surface acoustic wave on the piezoelectric substrate material is calculated by using the characteristic frequency analysis. The change law of the electromechanical coupling coefficient under the different thickness of different Si _ 2 films is analyzed. Secondly, by coupling the temperature field to the simulation model, the propagation velocity of the surface acoustic wave at different temperatures is calculated, and the change law of the film thickness and the temperature coefficient of the multi-layer film structure Si O2 is studied. and determining the thickness of the Si _ 2 film and the size of the electromechanical coupling coefficient corresponding to the zero-temperature coefficient of the multi-layer film structure. Finally, the S parameters of the multi-layer film structure sensor are obtained by frequency domain simulation, and the static test and verification of the device are carried out, and the electromechanical coupling coefficient measured by the multilayer film structure is much larger than that of the quartz crystal. The sensor prototype was fabricated by studying the MEMS processing technology. By using the dry etching process, the interdigital and reflective gate electrode structures are fabricated on the piezoelectric substrate. In order to solve the thermal stress problem of the large-thickness Si _ 2 thin film by PECVD, the problem of cracking of the surface of the Si _ 2 under the thick film thickness is solved by improving the process flow and using the method of releasing the thermal stress at the time of separation. in ord to reduce that size of the sensor and improve the sensitivity, an alloy diaphragm type force-transfer structure is designed. but due to the limitation of the process level, the sensor repeatability produced by the method is generally. In order to solve this deficiency, the 鈥渟andwich鈥，
本文编号：2383732
[Abstract]:Hydrocephalus is a common disease in infants and the elderly, the cause of which is the excessive or (and) circulation of the cerebrospinal fluid, which causes an increase in the intracranial pressure, resulting in an increase in the head, a headache, an intellectual disorder, and the like. At present, the method for treating the hydrocephalus mainly adopts a ventriculoperitoneal shunt, and the through-flow valve system is implanted in the patient, the excessive cerebrospinal fluid is drained into the abdominal cavity to be absorbed, so that the cranial pressure is kept in a normal range, the fault rate of the shunt valve system is high, the blockage is easy to occur, the problems of over-drainage or underdrainage and the like are serious, and the life safety of the patients is seriously threatened. At present, the size of the valve is mainly assisted by CT or MRI, but the method has the disadvantages of poor measurement precision, high cost and no continuous measurement. In view of the above shortcomings, this paper makes an in-depth study on the temperature compensation strategy, structural design method and processing technology of the sensor by means of sensor theory modeling and finite element simulation, based on the theory of surface acoustic wave, as the research object. and the low-cost continuous measurement function of the brain intracranial pressure is realized. In order to solve the problem of the temperature drift of the brain-cranial pressure sensor, the structure of the differential type brain-cranial pressure sensor based on the ST-cut quartz substrate is designed. As the ST-cut quartz has good temperature stability, the piezoelectric substrate of the sensor is used as the piezoelectric substrate of the sensor, and the interdigital transducer and the reflecting grating are formed by vapor-plating on the upper surface, and the resonator type structure is designed. In this paper, a method of combining the empirical formula with the coupled mathematical model is proposed, and the design efficiency of the sensor is improved. First, using the empirical formula, the structural parameters of the sensor are initially designed and the main value range is determined. and then the simulation design is realized more accurately by establishing a sensor coupling mathematical model. With the sensor S scattering parameter amplitude as the target, the parameters of the parameters such as the logarithm of the electrode finger of the sensor and the thickness ratio of the film were studied and the design was carried out to obtain the device with higher Q value. Finally, by designing the double-resonator type structure, the differential compensation of the sensor is carried out, and the temperature characteristic of the sensor is improved. The relative experiment of the sensor is carried out, the accuracy of the measurement is about 3.21%, and the design goal set forth in this paper is achieved. Because the electromechanical coupling coefficient of the ST-cut type quartz substrate is small, a new type of sensor for multi-layer film structure is designed by vapor-plating the Si O2 thin film on a 128-degree YX-cut Li Nb O3 piezoelectric substrate by using the characteristics of the opposite of the temperature coefficient of different materials. It has a large electromechanical coupling coefficient and good temperature stability. First, a finite element simulation model of the sensor is established, and the propagation velocity of the surface acoustic wave on the piezoelectric substrate material is calculated by using the characteristic frequency analysis. The change law of the electromechanical coupling coefficient under the different thickness of different Si _ 2 films is analyzed. Secondly, by coupling the temperature field to the simulation model, the propagation velocity of the surface acoustic wave at different temperatures is calculated, and the change law of the film thickness and the temperature coefficient of the multi-layer film structure Si O2 is studied. and determining the thickness of the Si _ 2 film and the size of the electromechanical coupling coefficient corresponding to the zero-temperature coefficient of the multi-layer film structure. Finally, the S parameters of the multi-layer film structure sensor are obtained by frequency domain simulation, and the static test and verification of the device are carried out, and the electromechanical coupling coefficient measured by the multilayer film structure is much larger than that of the quartz crystal. The sensor prototype was fabricated by studying the MEMS processing technology. By using the dry etching process, the interdigital and reflective gate electrode structures are fabricated on the piezoelectric substrate. In order to solve the thermal stress problem of the large-thickness Si _ 2 thin film by PECVD, the problem of cracking of the surface of the Si _ 2 under the thick film thickness is solved by improving the process flow and using the method of releasing the thermal stress at the time of separation. in ord to reduce that size of the sensor and improve the sensitivity, an alloy diaphragm type force-transfer structure is designed. but due to the limitation of the process level, the sensor repeatability produced by the method is generally. In order to solve this deficiency, the 鈥渟andwich鈥，
本文编号：2383732
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