Studies On Preparation And Annealing Treatment Of Silicon Rich Silicon Nitride Thin Films By PECVD

The quantum confinement effect of nano materials has been studied in the field of silicon based nanomaterials and their luminescence mechanism.Silicon based light emitting materials in silicon quantum dots was due to quantum confinement properties,in addition,the wavelength of the light quantum dots can scale with quantum dots changes,and it had a very good application prospect in optoelectronic devices.Silicon based materials containing silicon quantum dots were gradually introduced into solar cells.This will enable the effective absorption of solar light to enhance the efficiency of solar cells to improve photoelectric conversion,can become the future of the third generation of high efficiency silicon solar cell.Based on these advantages,in this thesis,silicon rich silicon nitride thin films were prepared by plasma enhanced chemical vapor deposition?PECVD?method,and the effect of deposition parameters on the structure of silicon rich silicon nitride thin films were investigated,luminescence properties of annealed films after annealing were also investigated,beneficial to the application of the optimal process parameters were obtained in the preparation of materials.In this paper,SiN_x thin films were prepared by RF-PECVD method.This method had the advantages of simple preparation method,low preparation temperature,high deposition rate,low energy loss and high production efficiency.The deposited thin film samples of X ray diffraction,FTIR,PL and UV-Vis absorption spectrum analysis,the influence of deposition conditions on the microstructure,crystallization,component content and luminescence properties of the films were investigated,silicon nitride and silicon rich silicon nitride films were prepared,then the silicon rich silicon nitride films were annealed.The results of this paper were divided into the following parts:1.The reaction gas source were Si H₄,NH₃,N₂,this paper study theinfluence of N₂ flow rate on the structure and properties of silicon nitride thin films.The experimental resulted show that a small amount of nitrogen into the film flow,Si-N bond concentration increased,nitrogen and silicon content ratio increases;continue to increase nitrogen flow,the film gradually rich nitrogen,with the increase of defect states,radiation enhancement,optical band gap broadening rapidly,with the tail state energy gradually decreased;the nitrogen content is higher,the formation of Si3N4 grains embedded in the amorphous Si N_x matrix,and the grain size increased gradually from the implementation of the amorphous SiN_x thin film material to process contains small crystallites of Si3N4.2.The reaction gas source were SiH₄,NH₃ and H₂.The influence of NH₃ flow rate on the preparation of silicon rich silicon nitride thin films was studied in this paper.The experimental resulted show that the number of N atoms and H atoms increases with the increase of ammonia flow rate,and the Si-H bond and Si-N vibrational strength increase.When the high nitrogen content,easy to form the dangling bonds of N,while the high electronegativity of N impact Si-H bond electron cloud distribution and to the high wave number direction of a blue shift,at the same time many structure defects on the film sample.The optical band gap was related to the defect density in the film,the more defects,the wider the optical band gap.With the increase of gas flow rate,the dangling bonds hydrogen saturation excess,was good for the formation of silicon nitrogen bonding,bonding film,the chemical bond density and the atomic density were monotonically increasing,the Si/N atom ratio varies between 0.903 and 0.994,gradually become thin film silicon rich silicon nitride materials.3.The reaction gas source were SiH₄,NH₃,H₂.Silicon nitride thin films were deposited by plasma chemical vapor deposition at low temperature.The samples were annealed in the annealing furnace and the annealing temperature were 500?,700? and 950?,annealing time of 90 minutes.The experimental resulted showed that the Si-H bond and N-H bond in the films were completely broken after 700? annealing,and the H film overflows.Si-H bond cleavage produces a large amount of silicon dangling bond,fracture and around thesilicon atom N-H bond to Si-N bond,Si-N bond in the film increased,while the peak also gradually to the high wave number direction,through the RBM model analysis showed that the silicon atoms are bonded to nitrogen atom number,and Si/N ratio fixed film that lead to more precipitation of silicon thin films.At510-550 nm,the emission band was caused by the confinement effect of the silicon quantum dots,and the defect state recombination in the films causes the appearance four emission peaks of P1,P2,P3 and P5.The growth of the silicon quantum dots with the annealing temperature led to the red shift and blue shift of the P4 emission peak.With the increase of annealing temperature,the Raman peak of the silicon quantum dots gradually approached to 500cm-1.The size of the quantum dots in the samples annealed at 700? and 950? temperature were calculated to be 3.01 nm and 3.05 nm.