WET ETCHING OF AL2O3 FOR SELECTIVE PATTERNING OF MICROSTRUCTURES USING AR-IMPLANTATION AND H3PO4( ION)

A new etching method for single-crystal Al2O3 is proposed using Ar+ im plantation and H3PO4 chemical etching. Photolitographically defined pa tterns are transferred into sharp structures on the wafer surface by s electively removing the damaged material. A double implantation of Ar at 50 keV followed by 180 keV was performed on all samples using a do se of 2 x 10(15) ions/cm(2) for the low-energy implant. Doses of 2 x 1 0(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 wer e used to characterize the pattern obtained, while transmission electr on microscopy and Rutherford backscattering channeling analysis were e mployed to study the implanted layer. Under the conditions investigate d, bath 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 degrees. Th e proposed method offers high selectivity, lack of contamination of th e substrate, and compatibility with standard processing.