Method for depositing a thin film on a substrate employing radio frequency excited gaseous plasma

摘要

Method for the deposition of thin films having high adherence, density, stability, absence of optical scattering and mechanical resistence characteristics.;It belongs to the field of thin film growth techniques (0.01 to 10 microns) for application to optics, integrated optics, microelectronics and metallurgy.;The method consists in the adoption of a system for the deposition under vacuum from a thermal source or electronic cannon and an RF power generator (13.6 MHz Radio Frequency) connected through an impedence adapter network to the substrate carrier which equips the deposition system.;The power of the generator allows to maintain a RF discharge in a gas input to the deposition system at a pressure of 1 10 mtorr.;Having a suitable condenser in series with the adapting network and the substrate carrier, it is in negative auto bias situation equal to about 45-48 % of the peak to peak RF discharge. This condition is imposed by the minor mobility of the ions compared to that of the plasma electrons and therefore also by the average electrical charge equal to zero on the electrodes of the RF discharge. In this situation the substrate resting on the substrate carrier is bombarded by the ions generated during the discharge and it simultaneously condenses the material evaporated by the thermal source or by the electron cannon.;This simultaneous bombardment at energies variable between 100 and 400 electron volts provides considerable improvements in the optical and mechanical characteristics of the films deposited.