Plasma etching of lead germanate (PGO) ferroelectric thin film

The lead germanate (PGO) thin film has been proposed for FeRAM devices, especially for one transistor ferroelectric memory cell application. To realize such applications, it is important not only to form the PGO thin film, but also to etch/pattern such thin film. In this work, plasma etching of PGO thin films was investigated by using chlorine or fluorine gas chemistries in an electron cyclotron resonance plasma reactor. Etch rates were studied as a function of etching conditions. The results indicated that a chemical effect, rather than a pure physical sputtering, was the dominant factor during the plasma etching of PGO material. It was also found that under the same etching conditions, a Cl2/Ar chemistry was more effective in PGO etching than a CF4/Ar chemistry. Under the etching conditions studied, there was no obvious plasma etching damage to the composition of the PGO thin films. However, the surface oxygen and chlorine concentration increased after the etching, indicating there might be some etch-induced surface residue. Such residue was thermally unstable, and can be greatly reduced by a postetch anneal in O2.