Methods of creation and effect of microwave plasmas upon the etching of polymers and silicon

Abstract

Although microwave stimulated plasmas have been studied for at least three decades, their implementation in microcircuit processing has been limited by their generation techniques. These limitations occur because the dimensions of commonly used resonant cavities are determined by the frequency at which the plasma is formed. Further, to maintain a high cavity Q, the diameter of the plasma must be smaller than the dimensions of the cavity. Even in the case where a waveguide is filled with a plasma, the plasma diameter is limited by the size of the waveguide. As a result, the typical dimensions of plasmas formed in these cavities are smaller than the dimensions of substrates undergoing plasma processing. Using techniques pioneered earlier which involve the use of surface waves, we show that microwave plasmas can be used to etch materials used in semiconductor processing, which compare favorably with typical R.F. (13.56 MHz) plasmas. © 1985.