Influence of a ground shield on heat flux in parallel-plate plasma system

The influence of a ground shield on the heat flux to a substrate in a parallel-plate plasma system was investigated experimentally using an original temperature measurement technique. The evaluation of the temperature rise curve shows that the heat flux from the plasma towards the substrate increases from 8% of the rf power to 26% by surrounding the powered electrode with the ground shield. The flux density on the powered electrode is 350 W m(-2) at an rf power of 50 W and pressure of 50 mTorr, and the value increases to 1150 W m(-2) by shielding. However, the total power into the electrode is 23-26% of the rf power in both cases, after accounting for the larger plasma facing surface area of the unshielded system. By shielding, a self-bias voltage decreases from 80% of the applied rf voltage to 73% due to a contracted spatial distribution of the electron density between the electrodes by shielding. The ion Bur is smaller than the heat flux obtained from the substrate temperature rise and it increases by shielding.