Effect of Number of Filaments on the Structure, Composition and Electrical Properties of μC-SI:H Layers Deposited Using HWCVD Technique

Influence of the number of filaments on the deposition rate, structural, compositional and electrical properties of hydrogenated microcrystalline silicon (μc-Si:H) deposited by hot wire chemical vapor deposition (HWCVD) has been studied. Also a systematic study of the variation of silane concentration in the silane + hydrogen gas mixture has been done for different number of filaments. The films are characterized by Raman and FTIR spectra to see the crystalline volume fraction and composition respectively. Dark and photoconductivity measurement have been done to see the electrical properties of the material. Cross section SEM and AFM studies also have been done to see their structure and surface morphology.The advantage of using 8 filaments is that the deposition rate of the μc-Si:H films is higher as compared to films deposited with 4 filaments without deteriorating the quality of μc-Si:H films. Some more interesting results are observed here. The post deposition oxygen uptake is lower for films deposited with 6 sccm and beyond silane flow for the 8 filaments case, while in case of 4 filaments the oxygen uptake is lower beyond 3 sccm silane flow. Another difference is that these films become totally amorphous for 8 sccm silane flow with 8 filaments while in case of 4 filaments the film becomes amorphous when 7 sccm silane flow is maintained. Thus it is confirmed that a higher number of filaments aid in the formation of crystalline film. Moreover the hydrogen content in films is also low with higher number of filaments.