No abstract

For one application of nonequilibrium oxygen plasma, low-temperature silicon trench oxidation is examined under the conditions of radio frequency bias as well as DC bias applications. The silicon oxidation has a very strong dependence on the substrate bias and is drastically reduced under the condition of no bias. The oxidation depth shows a maximum in a far downstream position from the microwave window. The silicon trench oxidation mapping clearly demonstrates that the maximum depth occurs along the line of the substrate bias of +20 V just above the plasma potential. In particular, silicon trench bottom oxidation is limited to higher radio frequency bias under the above conditions. It is concluded, for the reasons above, that the oxidation is due to the negative oxygen ions in downstream.