Diagnostic and Control of Silane Plasmas by Newlv Developed Radical Measurement Technique

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From a industrial point of view, lowering deposition temperature of silicon films are needed because process temperature sometimes limits substrate materials and process throughput. This project has two main purposes, i.e., firstly to develop new radical detection technique for diagnostic and control of silane plasma, and secondly, to produce high quality hydrogenated amorphous silicon and/or polycrystalline silicon by using a inductively coupled silane plasma (silane ICP).1.As a new diagnostic technique of SiH3 radical in silane plasma, we have developed ultra-violet transmission spectroscopy, which can detect SiH3 radicals and particulates in a silane plasma at the same time. This powerful tool is very simple and easy to apply for most of plasma reactors.2.We also succeeded in depositing high photoconductivity hydrogenated amorphous silicon and polycrystalline silicon at relatively low substrate temperatures of 40 and 250ﾟC,respectively. It is found that high quality films are deposited at high plasma density and low pressure plasma conditions. These conditions are quite different from those for capacitively coupled plasmas, because high rf powers or low pressures always degrades film properties in capacitively coupled plasmas. Plasma diagnostic by mass spectrometry revealed that silane molecules are almost completely depleted in the ICP and ion flux to the substrate is dominant compared with neutral radical flux.