Selective rate enhancement of etching processes by acoustic agitation

The authors introduce a novel method of etching materials in which an acoustic wave is introduced to agitate a selected area of a sample that is exposed to an etchant. A ZnO acoustic transducer is fabricated on one side of a material sample (glass or silicon). The other side is exposed to an etchant where up to 4 W of electrical power is applied to the transducer at 300-500 MHz. The creation of a variety of pits and trenches is shown on the etched sides of glass and silicon substrates without the use of masks. High-quality surface finishes are demonstrated. Etch-rate enhancement as high as 51:1 is shown, and this enhancement is characterized as a function of applied power. Efficient creation of holes is demonstrated by launching the wave through several layers of glass and etching all the way through the layer exposed to the etchant