This paper reports the formation of CZTSe absorber layers at temperatures between 380-550uC using a two-stage process. Energy dispersive X-ray spectroscopy (EDS) analysis identified the presence of Cu rich and Zn rich regions that are consistent with the presence of secondary phases. These phases could evolve at lower temperatures during the formation of the CZTSe phase. The absorber layers exhibit an evolution in the morphology with conversion temperature, with the highest temperature yielding the largest and most compact grains. In the past, Cu-Zn alloys have been identified in the sputtered metallic precursor produced with our baseline process. In this study, we investigate the selenisation of Cu-Zn precursors under the same conditions as used for the CZTSe in order to understand and identify the formation of potential secondary phases that might form in our CZTSe absorber layers. The results showed that Cu1·8Se and ZnSe were formed as separate phases. There is evidence to suggest that the Cu1·8Se evolves into the Cu2Se phase as the temperature increases above 520°C. This provides an insight into the phases formed during processing and their possible influence on kesterite formation.