Modified Photoresist Etch Mask Process for InP Channelled Substrate Lasers

We develop a new photoresist etch mask process to etch (001) InP wafers to obtain (111) B-faceted V-grooves for channelled substrate laser applications. We investigate the use of HCl and HF solutions to remove native oxide layers prior to V-groove etching. We also study the relationship between the photoresist mask undercutting and the bath temperature used for native oxide removal. The degree of undercutting in photoresist mask can be reduced about 2 times by increasing the HF bath temperature from room temperature to 48C during the oxide removal process. We also identify two important factors to control the mask undercutting rates as (a) the thickness of native oxide on InP surface and (b) the chemical reaction between InP and the oxide removal bath solution.