Study On The SiC And SiN_x Thin Films And Their Composite Antireflection Coating

Improving the conversion efficiency of solar cells has been a research focus of thephotovoltaic industry, antireflection coating formed on the surface of solar cells to improveits conversion efficiency is an effective way. At present, SiNxantireflection coating mainlyprepared by plasma chemical vapor deposition in the practical application of solar cellantireflection coating, but the production process has potential safety hazard due to the useof silane gas, magnetron sputtering method can avoid these problems and the amorphousSiNxthin films prepared in the low temperature environment, In addition, theantireflectivity of the double-layer antireflection film is better than single-layerantireflection film, and the SiC thin film with good optical, mechanical properties,radiation properties and passivation capabilities as solar cell window layer has been widelyused, making them to be the material of double-layer antireflection coatings and studyingtheir structure, morphology, mechanical and optical properties for improving the servicelife of solar cells have a great significance.In this paper, silicon nitride and silicon carbon thin films were prepared by RFmagnetron sputtering on quartz glass and stainless steel, a series of SiNxand SiC thin filmswere prepared by changing the sputtering time, sputtering power, working pressure andother deposition conditions. Useing a optical thin film design software TCFCAL designedSiC/SiNxdouble-layer antireflection coating, then the organizational structure, themechanical and optical properties of thin films were studied by scratch, UV-visiblespectrophotometer, X-ray diffraction (XRD), atomic force microcope (AFM), spectralellipsometer and other equipment. The results are shown as following.(1) There existed Si-N2-Si2bonding structure in the SiNxthin films, and the mainbond mode in the deposited SiC thin films was Si-C bonding structure, which maycontained Si-C-H bond. There existed amorphous structure and little microcrystallinestructure in the SiNx, SiC films and SiC/SiNxdouble-layer antireflection coatings, andthere was a weak (111) diffraction peak in the SiC thin films at the diffraction angle of35.6o, SiC/SiNxdouble-layer antireflection coating may contained diffraction peaks in thevicinity of diffraction angle at22°, SiNxand SiC thin films’ amorphous structure had high temperature stability after1000℃vacuum annealing.(2) SiNxand SiC thin films’ grains showed oval-shaped were growth of columnar orgranular within sputtering power of100~175W, and their surface structures weresignificantly improved by high-temperature annealing which also can greatly reducesurface roughness and helped refine the grains, then the more smooth and uniform densityof the excellent thin films could be formed. The effect of grain refinement of SiNxthin filmwas particularly evident when the sputtering power was125W. SiNxthin film emerged as agood film structure, uniformity particle size and good film density at different argonpressure intensities when the sputtering power was100W, SiNxthin film had more smoothcompact structure in the sputtering pressure of1.0Pa, the particle size of SiC thin filmswith sputtering power increased firstly and then decreased within sputtering power of75~175W, but under different conditions of argon pressure there had a maximum particlesize in the different sputtering power, and the particle diameter and roughness of SiC/SiNxthin films were become larger with the sputtering time increased.(3) SiNxand SiC thin films’ composite microhardness were on the rise with thesputtering power constantly increased, and their film-substrate cohesion also showed anincreasing trend. The hardness of the films changed significantly when the sputteringpower was150W, and the change curve of film-substrate cohesion similar regularity withthe composite microhardness.(4) SiN_x and SiC thin films growth rate increased with the sputtering power increasingwithin the sputtering power of75~175W, and the SiNxfilm growth rate increased linearlyfrom6.440nm/min increase to13.052nm/min, the SiC film growth rate increased slowedsuddenly in the sputtering power of150W. SiNxand SiC thin films’ refractive indexgradually become larger with sputtering power increased within the sputtering power of100~150W, the SiNxthin films’ refractive index varied maintained between1.72and2.25;and the refractive index of SiC thin films changed within the range of1.71~2.95, and therefractive index of it changed little at the lower sputtering power.(5) SiNxantireflection coating’s transmittance was good in the sputtering power of100W and the argon pressure of2.0Pa, while the SiC single-layer antireflection coating’stransmittance was good in the sputtering power of125W and the argon pressure of3.0Pa.SiNxthin film’s transmittance up to85%in the sputtering power of100W, while the SiCthin film had more excellent transmission performance in the sputtering power of125W,they both had a excellent transmission properties in the argon pressure of2.0Pa, and the transmittance of them declined after annealing.(6) SiC and SiNxthin film’s thickness respectively were76.4nm and106.8nm obtainedby the theoretical design, where the SiC/SiNxdouble-layer antireflection film had the besttransmission performance.