Etching process of back-illuminated ZnO ultraviolet focal plane array imagers

Etching process of back-illuminated ZnO ultraviolet focal plane array imagers was investigated. The etching result of 128 × 128 array, in which the area of unit cell was 25μm × 25μm, was studied. The profile angle was approximately 80°. There was a linear relationship between the etching depth and the etching time. The dependence of etching rate on NH₄Cl solution concentration was also studied. The photoresponsivity of the array's unit cells was measured. The UV-to-visible rejection ratio was around 60:1.