Improvement of dry etch-induced surface roughness of single crystalline β-Ga2O3 using post-wet chemical treatments

Post-wet chemical treatments using sulfuric acid and hydrogen peroxide mixture (SPM) or tetramethyl ammonium hydroxide (TMAH) solutions were performed to reduce dry etch-induced surface damage of beta-Ga2O3 caused by the inductively coupled plasma-reactive ion etching (ICP-RIE) process using the Cl-2/BCl3 gas mixture. The addition of BCl3 to the Cl-2/BCl3 gas mixture resulted in a significant enhancement of the etch rate of beta-Ga2O3 . However, it increased the surface roughness with the formation of the nonvolatile etch by-product B2O3 as a result of the BCl3/beta-Ga2O3 reaction. The post-SPM treatment led to the reduction of dry etch-induced surface damage of beta-Ga2O3 to a certain extent with the removal of B2O3. On the other hand, the post-TMAH treatment significantly improved the surface morphology of the dry etched beta-Ga2O3 surface. During the post-TMAH treatment, the chemical reaction between the damaged beta-Ga2O3 layer caused by ICP-RIE process and OH- in the TMAH solution led to the formation of the Ga oxide, followed by the simultaneous dissolution of the Ga oxide and the B2O3. Thus, the post-TMAH treatment effectively recovered the surface damage of beta-Ga2O3 induced by the ICP-RIE process using the Cl-2/BCl3 gas mixture.