Piezoelectric element, method for manufacturing piezoelectric element, and liquid ejection head

A liquid ejection head comprising a piezoelectric element,

• wherein the liquid ejection head eject liquid by driving the piezoelectric element,
• wherein the piezoelectric element includes:
• a substrate having a lower electrode, a piezoelectric film, and an upper electrode, in that order;
• and
• an insulating film that covers at least a side surface of the piezoelectric film,
• wherein one of side surfaces of the piezoelectric film has a plurality of step portions,
• wherein each of the plurality of step portions has a first side surface and a second side surface,
• wherein an angle of inclination of the first side surface with respect to an upper surface of the substrate is different from an angle of inclination of the second side surface with respect to the upper surface of the substrate,
• wherein an angle between the first side surface and the second side surface is 90° or more,
• wherein figures obtained by projecting each surface constituting the step portion in a film thickness direction do not overlap with each other, and
• wherein a width of the piezoelectric film in a direction perpendicular to the film thickness direction monotonically increases from the upper electrode to the lower electrode.

A method for manufacturing a piezoelectric element, the method comprising the steps of:

• forming a lower electrode on an upper surface of a substrate;
• forming a piezoelectric film on an upper surface of the lower electrode by forming a piezoelectric layer multiple times using a liquid phase method;
• patterning the piezoelectric film by wet etching;
• forming a metal film on an upper surface of the piezoelectric film;
• forming an upper electrode on the upper surface of the piezoelectric film by patterning the metal film by dry etching;
• processing a side surface of the piezoelectric film by dry etching;
• and
• forming an insulating film to cover at least the piezoelectric film,
• wherein the insulating film covers at least a side surface of the piezoelectric film,
• wherein one of side surfaces of the piezoelectric film has a plurality of step portions,
• wherein each of the plurality of step portions has a first side surface and a second side surface,
• wherein an angle of inclination of the first side surface with respect to the upper surface of the substrate is different from an angle of inclination of the second side surface with respect to the upper surface of the substrate,
• wherein an angle between the first side surface and the second side surface is 90° or more,
• wherein figures obtained by projecting each surface constituting the step portion in a film thickness direction do not overlap with each other, and
• wherein a width of the piezoelectric film in a direction perpendicular to the film thickness direction monotonically increases from the upper electrode to the lower electrode.