METHOD OF REDUCING REACTIVE ION ETCHING LAG IN DEEP- TRENCH SILICON ETCHING

摘要

PROBLEM TO BE SOLVED: To provide a method of minimizing an RIE lag, which occurs during production of a DT in a DRAM having a large aspect ratio. SOLUTION: Using this method, isotropic etching of a wafer can be prevented and hence a passivation film is formed to such a extent as to require to maintain a profile and shape of a DT in the wafer. The RIE process described here provides a partial DT etched in the wafer to attain a prescribed depth. This passivation film is grown to a certain thickness which is not sufficiently thick to block an opening of the deep-trench. In an alternative method, the passivation film is removed by a non-RIE process. The non-RIE process for removing the film may be wet etching using chemicals, such as hydrofluoric acid (buffered or unbuffered) or the like. Alternatively, a vapor phase of hydrofluoric anhydride or the like and/or un-ionized chemicals may be used. By controlling the film thickness, a prescribed depth of a DT for a high aspect ratio structure can be obtained.