Study On The Preparation Of Silicon Thin Film By CVD Method And Its Bonding With PDMS Substrate

As an emerging technology,flexible electronics was expected to break through the bottleneck of traditional electronic products.It used the classic structure of hard film/soft substrate to provide electronic products with complete functions while being flexible and malleable.In order to improve these characteristics,the classic structure had some improvements.The hard film buckling structure was one of the improved structures.This structure was a controllable buckling structure of corrugated morphology formed by bonding a hard film(such as metal or silicon film)to a pre-stretched flexible substrate and releasing prestress.The preparation of the hard film and the bonding of the film to the flexible substrate were all related to whether the hard film buckling structure can be formed.In this paper,silicon film is used as the hard film,and PDMS is used as the flexible substrate.Some related issues such as the preparation of silicon film by CVD method and the bonding between the silicon film and the PDMS substrate are explored.Firstly,the CFD method is used to simulate and analyze the inside of the tube furnace of the CVD equipment.The effects of different gas distribution parameters and deposition parameters on the gas flow field and film deposition rate in the reaction chamber are studied.Secondly,thin film deposition experiments are performed with using CVD equipment.The films are characterized by XRD,SEM and AFM.The effect of different deposition parameters on the film surface morphology and grain size was studied.Finally,the different process parameters of the plasma machine(RF power,air flow,modification time)are combined according to the orthogonal experiment table.The prepared silicon thin film and PDMS substrate are surface treated by plasma machine.Then irreversible bonding experiments are carried out to explore the combination of plasma machine process parameters when the bonding effect is the best.The main conclusions are as follows1.Improve the original solid furnace plug in the quartz tube of the tube furnace with a uniform opening method.The speed of the gas flow doesn't change suddenly when passing through the reaction chamber,and it won't cause impact when the film is deposited on the substrate surface.When the distance is 380mm,there is no phenomenon such as backflow and vortex in the gas flow in the reaction chamber,which can greatly improve the uniformity of the gas flow in the reaction chamber of the CVD equipment;single-factor simulation explains the deposition temperature,silane and nitrogen ratio two parameters Influence,when temperature is a variable,the deposition rate of the substrate surface increases with the temperature increase,and although the deposition rate at 9500C has a certain increase than that at 850? the increase rate of the deposition rate is the highest when 750? to 850?;When the mixed gas ratio is a variable,when SiH4:N2 increases from 1:4 to 2:3,the deposition rate increases,and then the SiH4 ratio is increased to 4:1,and the deposition rate changes very little.2.When the deposition temperature is 650?,there is no obvious characteristic peak in the XRD pattern of the film,which is an amorphous film.As the temperature gradually increases,the silicon grain size on the substrate surface gradually grows larger.At 850?,the surface silicon grains are densely distributed and uniform in size.When the deposition time is 60min,the characteristic peak half-width of the silicon film is small and the peak shape is sharp.As the deposition time continued to increase,the crystal phase content per unit thickness of the silicon thin film doesn't increase significantly.When the deposition time is 90min,the grain of the film is evenly distributed,and the surface of the film is smooth.As the proportion of SiH4 in the mixed gas increases,the silicon grain growth and silicon crystallization rate of the film increase.When the proportion of SiH4 is 2:3,the minimum Sq value of the surface roughness of the silicon film is 15.3nm.When the materials are different,the roughness values of the silicon thin films deposited on the copper foil and quartz glass under the same conditions are 15.12nm and 14.04nm respectively;which verifies the feasibility of depositing the silicon thin films on the copper foil.3.In the bonding experiment of silicon film and PDMS substrate,the evaluation criterion of bonding effect is that the bonding area is not less than 90%.To ensure the bonding quality,the bonding experiment should be completed within 10 minutes after the surface treatment is completed.From the experimental results,it is analyzed that the factors affecting the bonding area size are "Air flow>RF power>Cleaning time",and the optimal test scheme(the bonding area is the largest)has the process parameters of 350W,1.5L/min,2min.Each radio frequency section has a set of parameter combinations to make the PDMS substrate-silicon film bonding area meet the test requirements by adjusting the appropriate process parameters.This subject makes some improvements to the experimental equipment and solves the problems of the preparation of silicon thin films and the bonding with PDMS substrates.It has laid a solid foundation for experimental research and simulation analysis for the follow-up research of the research group.