Etch properties of gallium nitride using chemically assisted ion beam etching (CAIBE)

Dry etching properties of GaN were investigated using chemically assisted ion beam etching (CAIBE) with Cl-2, BCl3, and HCl gases. The measured GaN etch rate with increasing tilt angle showed the maximum at a 30 degrees tilt angle, similar to the effect of tilt angle on sputter yield. The GaN etch rate was the highest with Cl-2 and the lowest with BCl3. In the case or GaN etching with BCl3, the GaN etch rate was even lower than that in the case of GaN etched with Ar ion source only. The lower etch rate appears to be related to the higher binding energy of BCl3 and high degree of condensation on the substrate maintained at 0 degrees C. A highly anisotropic etch profile with smooth sidewalls could be obtained with Cl-2. The addition of Cl-2 to BCl3 did not improve GaN etch profile. The lowest roughness value of about 10 Angstrom was obtained for the etching with Cl-2. The GaN surface etched by Cl-2 and BCl3 showed an N-rich surface possibly due to the removal of Ga preferentially by forming GaCl4, and GaN surface etched by HCl showed near-stoichiometric surface possibly due to the removal of Ga by forming GaClx and N by forming NH4.