Growth And Application Of Thin Films Deposited By ICP-PECVD Method At Low Temperature Based On Siloxane Decomposition

With the development of technology and the improvement of people’s quality of life,flexible devices,wearable electronic devices,etc.have received widespread attention and rapid development.The various functional devices and materials that meet the needs of these devices have also undergone continuous improvement and innovation.Solid dielectric thin films play an important role as functional layers in these applications,and with the continuous expansion of applications,higher standards have been put forward for the performance and preparation methods of dielectric thin films.For example,in thin film packaging for silicon-based organic light emitting diodes（OLEDs）micro displays,in addition to meeting the packaging process temperature lower than the glass transition temperature of OLED materials,it is also necessary to consider the optical crosstalk problem caused by the extremely small pixel size of the device and the photolithography problem of implementing color filter films on transparent thin film packaging layers,There are more stringent requirements for the thickness,strength,and process temperature of packaging films.For example,in thin film transistor（TFT）backplane drive circuits used for flexible and transparent displays,the gate dielectric layer of TFT not only needs to have good insulation,but also needs to consider conditions such as transparency,Young’s modulus of materials compatible with flexibility,interface contact with the active layer,and the process temperature that the flexible substrate can withstand.For another example,for the Microfluidics devices in the application of wearable health detection devices,in order to efficiently collect the detected body fluid and quickly transport it to the test location,in addition to the bio-friendliness of the applied media film,the two main types of materials constituting the Microfluidics devices need to have super hydrophobic and super hydrophilic properties respectively,and the process temperature should be lower than the glass transition temperature of the flexible substrate.The common feature of the above applications is that the growth of the dielectric layer material needs to be carried out at lower temperatures.Although specific processes have been developed for the above applications,such as Atomic layer deposition（ALD）at a lower temperature,the scheme that combines growth efficiency and performance with alternative growth of organic/inorganic media layers has not yet been reported.The organic silicon precursor Hexamethyldisiloxane（HMDSO）can react with different proportions of O₂ to form inorganic SiO₂-like films or organic silicon polymers or a mixed structure of the two at lower temperatures,which is an effective method for low-temperature growth of dielectric layer materials.This paper expands the application field of this method by improving it and applying it to meet the requirements of the above applications.The work of this paper focuses on the deposition of high-performance inorganic and organic dielectric layers at lower temperatures through Inductively coupled plasma Chemical Vapor Deposition（ICP-PECVD）using HMDSO as the precursor to meet their application requirements on silicon-based OLED microdisplays,flexible transparent IGZO based TFTs and flexible Microfluidics devices,At the same time,the mechanism of the influence of the dielectric layer material grown by this method on the performance of various devices were explored.1.For the packaging of silicon-based OLED microdisplays,in order to achieve rapid deposition of submicron packaging films under lower temperature conditions for effective protection of devices,this paper proposes to use the ICP-PECVD method to grow SiO₂ layers and combine them with in-situ plasma oxidation treatment of nano thickness Al layers to achieve submicron level multi-layer composite film packaging,taking into account defects,reducing water vapor transmission paths,and increasing interlayer interactions in multi-layer structures.Firstly,HMDSO was used as the precursor to explore the optimal process conditions for depositing packaging films using ICP-PECVD in an environment below 100℃.A 600 nm single-layer SiO₂packaging film with a water vapor transmittance of 10^-3 g?m^-2?day^-1 was obtained,which is difficult to apply to OLED packaging.Subsequently,the oxygen plasma was used to react with the deposited Al layer in situ to generate Al₂O₃ and then combined with SiO₂film to form a composite encapsulation film,and the effects of plasma oxidation treatment time and the thickness of the Al layer oxidized by in-situ plasma on the performance of the encapsulation film were studied from the aspects of surface morphology,chemical composition and interfacial chemical bond existence of the film,and the water vapor transmittance was in the order of 10^-6 g?m^-2?day^-1,the visible light transmittance exceeded 90%,and the total thickness of the composite encapsulation film was 600 nm.It is found that the performance of SiO₂/Al₂O₃ multilayer thin-film packaging grown by this method is better than that of SiO₂/Al₂O₃ multilayer structure grown by other methods except ALD（the production efficiency of ALD is too low）,because the Al O_x layer and SiO₂ layer interface form Al-O-Si bonds under this process condition,which becomes the key to quickly forming high-performance thin-film packaging at lower temperatures.2.In order to achieve the preparation of gate dielectric films with low leakage current,low interface density of states,high breakdown voltage,and high visible light transmittance applied on transparent and flexible substrates for the application of TFT gate dielectric layers in driving circuits,this paper proposes to use Ar/O₂ hybrid plasma to treat single-layer SiO₂ gate dielectric layers under the guidance of improving the surface morphology and chemical composition of gate dielectric layers,And the idea of using organic silicon and SiO₂ to alternately cycle as gate media and allowing the organic silicon layer to come into contact with the active layer,appropriately increasing the H content in the active layer to obtain high-performance TFT devices.Firstly,using the HMDSO/O₂ reaction system and ICP-PECVD technology,SiO₂ thin films with different thicknesses were deposited at low temperatures（77℃）.Through the I-V characteristics and breakdown voltage of the MIM structure,a SiO₂ thin film with the lowest leakage current and a breakdown electric field exceeding 2.4 MV/cm was selected for IGZO TFT device research.A TFT device with mobility of 5.306 cm²/（V?s）was obtained as the basis for the study.Subsequently,different ratios of Ar/O₂ mixed plasma were used to treat a 250 nm thick SiO₂ gate dielectric film.When Ar/O₂ is100:60,the mobility of the TFT device is increased to 11.637 cm²/（V?s）without significant changes in other properties,and the interface charge trap density is reduced by an order of magnitude.The change of O 1s binding energy in the active layer is studied through XPS testing.Research has found that after plasma treatment,on the one hand,the roughness of the gate dielectric film is significantly reduced,and the smooth attachment surface makes the molecular arrangement in the IGZO film more orderly,reducing deep-level defects as carrier traps;On the other hand,molecules containing H are physically adsorbed on the surface of the oxygen-rich gate dielectric.During the sputtering deposition of IGZO,H attached to the surface enters the active layer of IGZO,serving as a shallow donor energy level,providing an electron for the conduction band,which is beneficial for improving the mobility of TFT devices.Afterward,by alternating organic silicon and SiO₂ as gate dielectric layers and contacting organic silicon with the active layer,a TFT device with a mobility increase of 15.596 cm²/（V?s）and a decrease of three orders of magnitude in interface charge trap density was obtained.Research has found that a portion of H in organic silicon can passivate defects in gate dielectric films,while another portion enters the active layer to increase carrier concentration,effectively improving TFT performance.3.In the application of wearable health monitoring devices,in order to achieve efficient collection of tested samples at low temperatures while also preparing a non-toxic and harmless super wetting surface for the human body,this paper proposes the idea of using microspheres naturally present in HMDSO deposited films as primary microstructures and using soluble Na Cl and sucrose grains as templates for secondary microstructures to prepare super wetting surfaces with secondary microstructures.Firstly,a superhydrophilic surface with a contact angle of 7°was obtained by reacting HMDSO with O₂ to generate SiO₂ thin films.Then,the feasibility of using secondary microstructures to achieve superhydrophilic surfaces was calculated based on the wetting theory.Subsequently,thin films with secondary microstructures were prepared using copper mesh masks,but it was difficult to obtain superhydrophobic surfaces due to processing accuracy issues.Afterward,the secondary microstructure was prepared using soluble Na Cl grains and sucrose grains instead of copper mesh masks for optimization,and a superhydrophobic surface with a contact angle of 158°was obtained.Due to the solubility of Na Cl and sucrose grains in water,it provides a certain reference value for the implementation of superhydrophobic/hydrophilic surfaces with high visible light transmittance.