Study On Radiofrequency Plasma Oxidation Process Diagnosis

In the semiconductor industry,the plasma enhanced chemical vapor deposition technology(PECVD)is widely used in the preparation of uniform low temperature coatings.However,the development process of the film is mainly based on the experimental verification method because the plasma mechanism in vacuum coating technology is very complicated.It makes the development of the film very low efficiency.In addition,vacuum coating technology is still there is uneven film and unstable film quality.In this paper,the plasma oxidation process was studied by using Langmuir probe diagnosis and emission spectroscopy.The model of plasma oxidation and process parameters is established for the study of PEM control system.This paper built the Langmuir probe diagnostic system driving device,using ball screw and stepper motor drive device of the probe,to probe the axial position of Langmuir changed to multi point measurement of plasma.We focus on the plasma oxidation process of PECVD using Langmuir probe diagnostic device and optical emission spectrometer.The mixture of Ar and O2 was used in the experiment.The plasma density,electron temperature and micro parameters of the plasma are studied by means of plasma diagnostics.The results show that the plasma is composed of excited Ar and O atoms,Ar+and O2+,except for the ionized molecules and atoms.The increase of RF power will increase the ionization rate of the gas,and the amount of Ar/O atoms in the excited state,Ar+and O2+will increase gradually.But when the electron density in the plasma increases,the electron temperature decreased,while the average electron energy will become saturated,the change of electron density in the plasma will tend to smooth.It was found that the plasma between the parallel plate electrodes of the device was unevenly distributed in the direction of the probe axis,and the plasma density in the central region was lower than that at the edge of the plate.This phenomenon is verified by the XPS test.Mainly due to the radial drift diffusion of plasma,the uneven distribution of gas and the edge effect led to the phenomenon.Combined with this phenomenon,simulation software was used to simulate the gas flow and the electric field near the discharge plate,and the suggestions of improving the plate structure were put forward.At the same time,the effect of the gas flow ratio on the plasma composition was studied experimentally.It is considered that the gas flow rate and the proportional choice have great influence on the content of excited atoms.Reasonable choice of gas flow and proportion,to improve the surface quality of the workpiece has an important impact.