| Plasma in radio frequency (rf) glow discharge is widely used in the preparation of semiconductor film materials and microelectronic industry. The diagnosis and measurement of the primary particles in deposition and etching process make it better to understand the mechanism of film deposition and etching, which can improve the qualities and characteristics of thin films. Mass spectroscopic analysis is a simple and useful technique for plasma diagnosis. And it is superior to optical spectroscopic diagnosis in identification of plasma components and measurement of particles concentration in plasma vapor reaction and interaction between plasma and surface.Mass spectrometer must be operated under a high vacuum environment because of its particular conformation and operation principle. This makes it only detect specimen sampled from a fixed position of plasma bulk, such as near the discharge chamber wall or discharge electrodes. Until now, no spatial distribution of particles in plasma has been measured simultaneously by means of mass spectroscopy analysis.In this paper, we propose and establish a movable mass spectroscopy gas sampling apparatus with sufficient simplicity and reliability to be suitable for mass spectroscopic sampling. The sampling position can be moved easily along the central symmetry axis of two electrodes by adjusting the relative height of the two coaxial polytetrafluoroethylene ( PTFE) tubes. Thedepletion fraction (f) of plasma is a key parameter for calculating the neutral radical density, wepropose a straight-line fit method with sufficient reliability and precision for deducing / on thefoundation of previous study.For the simplicity of argon atom structure and physical chemistry property, we detect and diagnose Ar plasma by means of mass spectroscopic analysis at first. We propose a new method to obtain the depletion of monatomic molecular gas plasma, and study the spatial distribution of Ar plasma depletion fraction, the effect of discharge power and pressure to Ar plasma depletion fraction, and the spatial distribution of Ar+ signal.We measure the spatial distribution of SiH_n (n=0-3) radicals, which are dominant precursors in formatting amorphous silicon film, by means of mass spectroscopic analysis. We propose astraight-line fit method to obtain the depletion fraction of XYn gas plasma. The method is more universal and more accurate than the previous one. The relative abundances of SiHn (n=0-3) radicals are calculated by using the depletion fraction of SM4 plasma. The results demonstrate that SiH2 and SiH3 are the most dominant precursors in deposition amorphous silicon film. Te spatial distribution of SiHn( n=0-3 )radicals appear that the densities of SiHn( n=0-3 )radicals have the peak values at or near the middle position of two electrodes.We also measure the spatial distribution of SiCln (n<3) radicals, which are dominant precursors in formatting polycrystalline silicon film, by means of mass spectroscopic analysis. The results appear that Si is the most abundant radical in SiCLj, then is SiCl, and S1CI2 is less than SiCl. This reveals that Si and SiCl may be the primary precursor in forming the polycrystalline silicon films. The densities of the SiCln (n<3) radicals have the peak values at the 1/3 position of the electrode space away from the rf powered electrode along the axial orientation; the density of Si and SiCln (n=l,2) has the peak values away from axis of two electrodes 25mm and 7mm along the radial orientation, respectively. We also study the effects of power, pressure and flow rate to SiCln (n<3) radicals. It is found that the Si density is increasing with increase of power, and SiCln (n=l,2) densities are decreasing with increase of power in the range of 2-10W, and not having notable change under high power of 10-40W; the SiCln (n<3) densities are increasing with increase of pressure, and decreasing with increase of flow rate, then increasing slightly under high flow rate (> 13 seem).The experimental results and analysis demonstrate that the proposed straight-line fit method is more universal and more accurate for deducing the plasma depletion fraction than the previous one, and the proposed and established movable gas sampling apparatus is suitable for detecting the spatial properties of plasma, which provides useful experimental data for researching thin film deposition and etching mechanism.
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