Study Of Low Temperature Plasma Enhanced Chemical Vapor Deposition And The Preparation Of Si₃N₄ Thin Film

The nanometer thin film is paid great attention now. Compared with the common thin film, it has some unique properties such as huge conductance, huge magnetism resistance effect, huge Hall effect and so on. The nanometer silicon nitride thin film is a kind of medium film with excellent physical and chemical properties. The film prepared by ICP-PECVD has the good properties of thermal stability and dielectric characteristic, and has been widely used in many fields such as the microelectronics industry.In this paper we mainly study on the technics of inductively coupled plasma enhanced chemical vapor deposition (ICPECVD) and the properties of the silicon nitride thin film. With the aid of the distribution of the plasma parameter, the proper technical parameters are selected to prepare the silicon nitride thin film. The thin film prepared are detected by the infrared spectrum instrument, X ray diffraction instrument and the atom force microscope. The way in which the properties of the thin film can be improved is explored.The quality of the silicon nitride thin film depends mostly on the plasma parameters. In this paper, the ion density distribution (Ni )in the tubular reaction chamber was diagnosed by a Langmuir single probe. The distribution rules of ion density in the axial and radial direction in the reaction chamber were obtained. The ion density increases with the increasing of the RF power. Also, the ion density will firstly increases with the gas pressure in the chamber, then drops again. When the RF power is 150W and the gas pressure is 16Pa, the maximum of the ion density is 3.85×l010cm-3, which is higher than those under the conditions of 100W. When the RF power is 100W, the ion density will increase with the increasing of the gas pressure. When the gas pressure is 10Pa, the ion density reaches its maximum 2.20 ×10¹⁰ cm-3. After that, the ion density drops with the increasing of the gas pressure. The regions with uniform ion density distribution were also obtained, which is very useful to the deposition of thin film.The thin films are detected by the infrared spectrum instrument, X ray diffractioninstrument and the atom force microscope. The results show that the clearly pronoumced peak at 891cm-1 indicates the Si-N bond of the crystal Si3N4. There are also Si - H and N-H bonds because of the existence of hydrogen as impurity. The silicon nitride thin film prepared on the substrate of crystal KBr has a β- Si3N4 hexagonal crystal structure and that prepared on the silicon has a a-Si3N4 hexagonal crystal structure. The microscopic structure of the thin film deposited on he silicon is observed with the atom force microscope.