Motoyuki Ono

Temperature rise in a birefringent substrate caused by RF discharge plasma

Temperature rises of a birefringent substrate (LiNbO3) have been measured in an argon RF discharge plasma. The measurement method is based on monitoring the variation of natural birefringence with temperature by laser interferometry. Using this method, the dependence of substrate temperature rise on applied RF power and gas pressure has been investigated. The evaluation of the temperature curves shows that heat flux from the plasma toward the substrate is independent of time and temperature. The magnitude of the flux differs largely from the applied power, and is approximately 0.4% of the power. By measuring the electron density, electron temperature, and plasma potential with a Langmuir probe, the energy of the ions incident on the substrate is estimated. The ion flux toward the substrate is calculated from the energy of ions and is compared with the measured heat flux. The dependence on the applied power is in approximate agreement between those fluxes. The temperature distribution over the substrate thickness is simulated numerically using the finite difference method.