Comparison Of Dry And Wet Etch Processes For Patterning SiO2/TiO2 Distributed Bragg Reflectors For Vertical Cavity Surface Emitting Lasers

A dry etch process for patterning SiO sub 2 / TiO sub 2 distributed Bragg reflectors (DBRs) for vertical cavity surface emitting lasers (VCSELs) was demonstrated. The etchings were conducted using an inductively coupled plasma system. Both SF sub 6 / Ar and Cl sub 2 /As based etching chemistries were investigated. Very slow etch rates were obtained for TiO sub 2 when using a Cl sub 2 / Ar chemistry due to the low volatility of the etch products, TiCl sub x. Using an SF sub 6 / Ar based chemistry, similar etch rates for TiO sub 2 and SiO sub 2 were obtained, which is desired for etching through the alternating SiO sub 2 and TiO sub 2 layers of the DBR. An average etch rate of 1200angstroms/min was achieved at ICP and rf powers of 500 and 245W, respectively. Wet chemical etch processing was also explored using a buffered oxide etchant and diluted HF. Etch rates of 1200 and 200angstroms/min in dilute HF solution were obtained for TiO sub 2 and SiO sub 2, respectively. However, a significant etch-undercut of the DBR structure and delamination at the SiO sub 2 / TiO sub 2 interfaces, due to internal stress created between these layers, were observed when these wet etchants were used.