The Study On Degradable Controllable Monitoring Design Of Implantable Device Package Structure

In recent years,with the rapid development of electronic technology,the application fields of microelectronic technology have gradually changed,from the traditional three fields of"computer,communication and information processing"to"energy,health and environmental protection",and implantable devices have emerged as the times require.Due to the advantages of flexibility and biocompatibility,implantable devices are widely used in communications,wearable electronics,and environmental monitoring.They also play a more and more important role in the fields of biology,medicine and defense.Since the implantable device is located in the living body for a long time,the p H value of the local microenvironment,temperature and ion changes will affect the performance of the device.In addition,implantable devices are mainly for biomedicine,which puts forward new requirements for their controllable insights.Therefore,selecting the appropriate packaging structure and packaging technology,which can ensure that the implantable device can play functions normally in the living body,and at the same time,they can degrade in time,is particularly critical.For these reasons,in order to achieve controllable degradation of implantable devices,this paper focuses on the growth and preparation of five kinds of packaging layers,as well as the degradation characteristics of different materials,include silicon nanomembranes(Si NMs),silicon dioxide film(Si O₂),silicon nitride film(Si₃N₄),and alumina film(Al₂O₃).In addition,we also prepared the silicon nitride film(Si₃N₄)packaged magnesium resistor and explored the structural design,key preparation process and resistance characteristics of the magnesium resistors.The main results are as follows:By establishing the reaction diffusion theory and solving the diffusion equation,the paper obtains the relationship between film degradation rate,the diffusivity of the encapsulation layer in solution,the molar mass of the encapsulation layer,the mass density of the solution,the concentration of the solution,the number of water molecules reacting per atom of the encapsulation layer and the thickness of the encapsulation layer.The effects of temperature and p H value on the degradation rate were analyzed.The results showed that the higher the temperature,the faster the degradation rate and the stronger the alkalinity,the faster the dissolution rate of the Si NMs.Through the analysis of the Arrhenius equation,it is confirmed that that the degradation rate of the film at the biological body temperature can be calculated by accelerated experiment.Based on various influencing factors of degradation rate,this paper proposes a controllable monitoring design idea:explore the influence of external factors on the degradation rate of packaging materials through different environmental temperatures and different solution types;study the influence of its own factors and the degradation rate of packaging materials through design thickness and packaging shape.The thickness and shape of the packaging materials were designed by analyzing the flexural property,light transmittance and resistance of the nanofilms.For the preparation of Si NMs,we propose to dry etch the top silicon layer of the SOI structure and wet etch the buried oxygen layer.And then the top layer of Si NMs is transferred onto a flexible substrate through the combination of stamp transfer and adhesive coating.According to these methods,we designed the etching hole on the top layer of the silicon-based thin film and the layout suitable for the transfer process.Then we determined that the reactive ion etching(RIE)rate of the top silicon film of SOI was 6nm/s.By comparing the relationship between the etching solvent of the buried oxide layer Si O₂ and the etching,the method of pure hydrofluoric acid(HF)etching for 1 hour was selected.In the PECVD preparation of Si O₂film,through the exploration of the pressure in the cavity and the power of the RF source on the growth rate,the optimal process parameters of the PECVD preparation of Si O₂film and Si₃N₄ film are presented.In addition,the Al₂O₃ film was prepared by PEALD technology,the roughness was 0.35 nm,and the surface uniformity was good.In the degradation experiment,by comparing the effects of different environmental temperatures on the degradation rate,it was found that the Si NMs showed good degradation characteristics in PBS solution at p H 7.4,and could achieve a controlled degradation in hours to tens of hours.And the higher the temperature,the faster the degradation rate,this experimental phenomenon is consistent with the theoretical basis.Through experiments,the degradation rate of Si NMs in PBS solution at 70?is 93 nm/day,and the degradation rate at 50?is 20 nm/day.The degradation rate of silicon nanofilm in PBS solution at 37?is about 6.77nm/day.In addition,a degradation experiment of Si NMs in artificial sweat at37°C for three weeks was carried out.The surface morphology and thickness of the Si NMs did not change significantly,confirming that the Si NMs hardly degrade in acidic solutions.Comparing the effects of different solution types on the degradation rate,HBSS solution is more likely to accelerate the degradation of silicon substrate than PBS solution.By comparing the effects of different package shapes on the degradation rate,it is obtained that the strip shape is easier to accelerate the degradation of the substrate than the XD type.By analyzing the degradation of Al₂O₃ film,the degradation rate in 50°C PBS solution was 0.16nm/h.In this paper,we designed three types of serpentine resistor layouts with different lengths.Magnesium resistors with Si₃N₄ film as the encapsulation layer are prepared by electron beam evaporation(E-beam)and PECVD techniques.A PDMS reaction chamber and a real-time electrical monitoring model are designed.These studies provide a good practical basis for the next step of real-time monitoring.