Low Temperature Growth Of Silicon Carbide Films Containing Nitrogen With High-density Helicon Plasma

Coating material for ware and corrosion resistance is a new kind of functional material with special physical and chemical properties,which is widely used in fields of mechanical manufacturing,high-tech,aerospace and national defense construction,etc.In aerospace,aluminum matrix composite reinforced by silicon carbide particles(SiCp/Al)has been applied in aerospace vehicles as the main load-bearing structure,because of its excellent performance and low cost.There are many kinds of wear-resistant and corrosion-resistant coatings,being widely used and forming a large-scale high-tech industrial cluster,which have very broad market prospects and play a very important supporting role in realizing the great strategy of"Made in China 2025",as well as the intelligent upgrading of manufacturing industry.SiCN_x films possess both SiC and SiN excellent characteristics,with good application prospects as protective coatings for their excellent heat resistance,high temperature creep resistance,oxidation resistance,low friction coefficient,corrosion resistance and bending strength.However,the preparation process of SiC and SiCN_xfilms still needs to be optimized.Firstly,the traditional PVD process has the disadvantages of strict equipment requirements,high cost,uneven coating on the surface of complex structures,and slow speed.Due to the limitation of target size,it is difficult to coat large-scale workpieces.Besides,the traditional CVD process has some shortcomings,such as high process temperature(usually500-1000?),flammable and explosive precursors,which limit the application of SiC and SiCN_x films.To resolve the above problems,a new method of preparing SiC and SiCN_x films by CVD process under the Helical Wave is presented in this paper.High energy density produced by helicon wave plasma can rapidly prepare films at low temperature.A series of nitrogen-containing precursors with different structures are designed to study the growth of SiCNx films,which simplify the process and improve the safety.By studying the structure of precursors,the structure-activity relationship between precursor structure and composition&properties of films was revealed from the molecular point of view.The concrete methods are described as follows.(1)First of all,verify the feasibility of the method.Using Si(CH₃)₄as the precursor,the technological conditions for the growth of SiC films by CVD under the action of helical wave were studied.The results show that from this method SiC films can be successfully formed at low temperature,with fast films forming speed and high quality.The bias voltage of the deposition process affects the composition and properties of the films.The hardness of the films increases with the increase of bias voltage.(2)Then,we study how to prepare SiCN_x films safely and rapidly at low temperature under the action of helical wave.First step,we designed,synthesized and characterized a series of new nitrogen-containing organoguanidine silane compounds.The thermal stability,volatility and film-forming properties were studied.The results show that organoguanidine silane compounds have excellent thermal stability and good volatility and are sui Table for the study of the growth of SiCN_x films as precursors of CVD under the action of helical wave.(3)Besides,we have studied and explored the growth process of SiCNx thin films.SiCNx films were successfully prepared by using organoguanidine silane precursors.The film forming temperature was below 150?and the deposition rate was fast(up to 36nm/s).The results show that the nitrogen content in the film can be adjusted by the nitrogen content in the precursor.The hardness and refractive index of the films decrease with the increase of nitrogen content,while the surface roughness and friction coefficient increase with the increase of nitrogen content.(4)Last but not least,the relationship between process conditions and composition&properties of SiCNx films was studied.With the increase of bias voltage,the contents of Si,C,N and various bond states in the films changed correspondingly.Under high bias voltage,diamond phase C-C sp³bonds will be formed,thus forming a compact network structure and improving the mechanical properties of the films.If the bias voltage increases,the friction coefficient and surface roughness will decrease,but the hardness and refractive index will increase.However,too high bias voltage will produce negative etching effect and reduce the film performance.