AN ELECTRON-CYCLOTRON RESONANCE PLASMA SOURCE

The further development of semiconductor technology calls for low energy, high power plasma sources is considered. An electron cyclotron resonance (ECR) plasma source developed by Leybold fulfils the necessary requirements for 200 mm wafer processing and allows the generation of both isotropic and anisotropic etching profiles at low ion energies. This source is designed for application in a single-wafer-etching device using reactive gases. Since the source is designed for the etching of up to 200 mm substrates, it is necessary to maintain a homogeneous plasma over a large area. This has been achieved by a fully rotational symmetric construction of the source as well as by microwave coupling into the plasma via a horn-shaped radiator. The process developments at present being carried out are concentrating on the etching of SiO2, phosphosilicate glass, polycrystalline silicon and single-crystal silicon using gases of different chemical composition based on fluorine, chlorine and bromine chemistry. Furthermore, the applicability of the source for etching III-V compounds is shown. The application potential using an ECR plasma source will be demonstrated in detail by a polycrystalline silicon etch process. In this case the choice of low pressure operation allows polycrystalline silicon to be etched anisotropically using pure chlorine without side-wall passivation being required.