Issues regarding the high rate afterglow and direct plasma etching of silicon

Chemical etch rates of silicon have been determined in a flowing afterglow of reactant and in a direct plasma etching system. Direct plasma treatment was carried out in a parallel-plate etch system with 13.56-MHz excitation and substrate temperature in the range of 23 degrees C to 350 degrees C. Afterglow processing was performed using species generated in a microwave-excited plasma tube. These species were allowed to react with the silicon in a remote thermal process zone at temperatures similar to those used in the parallel-plate system. Silicon etch rates as high as 47 mu m/min have been achieved with selectivity to SiO/sub 2/ of 25, using NF/sub 3/ as the fluorine precursor. The implications of the results with regard to the precursors and the ambient conditions are discussed for each case. In addition, the use of masking materials such as photoresist, SiO/sub 2/, and aluminium is considered. This high-rate etching of silicon provides a productive fabrication option in cases where device structures require large amounts of silicon to be removed.<>