Measurements of heat flux distribution toward substrate by means of the LiNbO3 interferometer, and electron density in a capacitively coupled rf discharge plasma

Measurement of temperature by the laser interferometry method with a LiNbO3 substrate and determination of heat flux in capacitively coupled plasma (CCP) are described. This method is based on monitoring the variation on nature birefringence with temperature. The CCP is generated at 20 or 40 mm gap length, 100 mTorr argon gas pressure, and 250 cc/min gas flow with an rf input power of 100 W. The rf power is supplied to the lower electrodes through a L-type matching network containing a coupling capacitor and the upper electrode is grounded. The heat flux and electron density distribution possess the same peak characteristics around the maximal point of plasma density under the same experimental conditions. The average diffusion flux for electrons and ions can be calculated from the electron distribution and ambipolar diffusion coefficient. The axial and radial diffusion fluxes are 2.4 x 1012 and 8.1 x 1012/cm2 s, respectively. Taking account of the electrode and side area, we find that the total axial flux is 10 times larger than the radial one