In an embodiment of the present invention, a method is provided of patterning PZT
layers or BST
layers. For example, a PZT layer or a BST layer is
plasma etched through a high-temperature-compatible
mask such as a
titanium nitride (
TiN)
mask, using a
plasma feed gas comprising as a primary etchant
boron trichloride (BCl3) or
silicon tetrachloride (SiCi4). Although BCl3 or SiCl4 may be used alone as the etchant
plasma source gas, it is typically used in combination with an essentially
inert gas. Preferably the essentially
inert gas is
argon. Other potential essentially
inert gases which may be used include
xenon,
krypton, and
helium. In some instances O2 or N2, or Cl2, or a combination thereof may be added to the primary etchant to increase the etch rate of PZT or BST relative to adjacent materials, such as the high-temperature-compatible masking material. A
TiN masking material can easily be removed without damaging underlying oxides. The selectivity of PZT or BST relative to
TiN is very good, with the ratio of the etch rate of the PZT film to the etch rate of the TiN
mask typically being better than 20:1. In addition, the etch rate for PZT using a BCl3-comprising plasma source gas is typically in excess of 2,000 Å per minute. A substrate bias power is applied to direct ions produced from the BCl3 or SiCl4 toward the surface to be etched. The bias power is controlled to avoid
sputtering of a conductive layer or
layers in contact with the PZT layer, so that the surface of the etched PZT is not contaminated by a conductive material, which can cause the
semiconductor device which includes the patterned PZT to short out.