Wet etching of Al2O3 for selective patterning of microstructures using Ar+ ion implantation and H3PO4

A new etching method for single-crystal Al 2 O 3 is proposed using Ar + implantation and H 3 PO 4 chemical etching. Photolitographically defined patterns are transferred into sharp structures on the wafer surface by selectively removing the damaged material. A double implantation of Ar + at 50 keV followed by 180 keV was performed on all samples, using a dose of 2 x 10 15 ions/cm 2 for the low-energy implant. Doses of 2 x 10 15 , 2 x 10 16 , and 4 x 10 16 ions/cm 2 were used for the 180 keV implant. Scanning electron microscopy and atomic force microscopy were used to characterize the pattern obtained, while transmission electron microscopy and Rutherford backscattering channeling analysis were employed to study the implanted layer. Under the conditions investigated, both the etchable range (90 to 160 nm) and the etching rate (1 to 7 nm/min) were found to be strongly correlated with the implanted dose. Sharp and uniform interfaces between etched and unetched regions were obtained, forming steps with an average slope of 30 to 45°. The proposed method offers high selectivity, lack of contamination of the substrate, and compatibility with standard processing.