Material Properties And Etching Effects Based On SiF₄/H₂/Ar Gas Mixtures In PECVD

Silicon thin films, as part of the 2nd generation photovoltaic technologies, offer outstanding advantages and promising properties. Usually, the fabrication technique of silicon thin films is Plasma Enhanced Chemical Vapor Deposition(PECVD) with Si H4/H2 gases. In LPICM(Physics Laboratory of Interfaces and Thin Films), however, a different technique based on Si F4/H2/Ar gas mixtures in PECVD has been developed to fabricate silicon thin films with excellent properties, and a phenomenological model revealing the Si F4/H2/Ar plasma process has been proposed. This model is of great significance for determining the deposition conditions to fabricate thin films with desired microstructures and properties.To further confirm this model, investigate the factors that affects the film microstructure and finally improve the performance of solar cells, a series of experimental studies concerning the incubation time, crystallite size and crystallization mechanism of microcrystalline silicon thin films has been conducted in this paper. A crystallization mechanism related to nanoparticles generated in the plasma phase is tentatively proposed, and information on typical size and volume desity of the nanoparticles are obtained.Many experimental researches are focusing on microsrytalline silicon thin film solar cells, by solely using experimental methods, however, might be aimless sometimes. Besides, experiments are usually time-comsuming and not very cost-efficient. Therefore, in this paper, software SCAPS-1D is used for simulation research focusing on the crystalline volum fraction(Fc) of intrinsic ?c-Si:H layer which is often changed with deposition conditions, and the effects of parameters related to Fc on the performance of solar cells are discussed. Parameters related to the high VOC of fully crystallized ?c-Si:H,F solar cells are also found.In the PECVD processes, the ratio of Si F4/H2 concentration is often changed to obtain materials with different properties, and either excess Si F4 or H2 could have etching effects on the layers. The amorphous silicon layers and monocrystalline silicon wafers are employed to illustrate how the etching affects the materials quality, particularly the surface morphology. In each individual etching process, two identical silicon substrates are placed on the grounded and RF electrodes of the PECVD reactor respectively, to study the effects of maximum Ion Bombardment Energy(IBE) on the etching results.