We present an optimized grating formation process on InP substrates by using holographic lithography and a chemical etching. Process parameters associated with the developing and the etching were varied to ensure a reliable and reproducible fabrication condition. A quantitative experimental study of the variation of the grating shape with different fabrication conditions is presented and its optimization is discussed. 1.55 mu m distributed feedback lasers were fabricated using an optimized grating formation process and lasing characteristics showed that the formed gratings are quite uniform and reproducible.