Bulk acoustic wave resonator and method of manufacturing the same

A method of manufacturing a bulk acoustic wave resonator, the bulk acoustic wave resonator comprising a substrate, a lower electrode disposed to cover at least a portion of the substrate, a piezoelectric layer disposed to cover at least a portion of the lower electrode, an upper electrode disposed to cover at least a portion of the piezoelectric layer, and a passivation layer disposed to cover at least a portion of the upper electrode, the method comprising:

• forming a photoresist (PR) trimming mask of a photoresist on a portion of the passivation layer disposed in a region of the bulk acoustic wave resonator in which a trimming operation is not to be performed on the passivation layer;
• trimming a portion of the passivation layer disposed in a region of the bulk acoustic wave resonator in which the trimming operation is to be performed on the passivation layer;
• and
• removing the PR trimming mask.

A bulk acoustic wave resonator comprising:

• a substrate;
• a lower electrode disposed on at least a portion of the substrate;
• a piezoelectric layer disposed on at least a portion of the lower electrode;
• an upper electrode disposed on at least a portion of the piezoelectric layer;
• and
• a passivation layer disposed on at least a portion of the upper electrode,
• wherein portions of the lower electrode, the piezoelectric layer, and the upper electrode overlap to form an active region of the bulk acoustic wave resonator,
• the passivation layer comprises:
• a first portion disposed outside the active region and having a first thickness;
• and
• a second portion disposed in the active region and having a second thickness less than the first thickness, and
• a transition between the first thickness and the second thickness occurs over a distance that is sufficiently small to prevent an abnormal region of amplitude fluctuation caused by the transition from occurring in a resonator waveform of the bulk acoustic wave resonator.

A method of manufacturing a bulk acoustic wave resonator, the bulk acoustic wave resonator comprising a substrate, a lower electrode disposed on at least a portion of the substrate, a piezoelectric layer disposed on at least a portion of the lower electrode, an upper electrode disposed on at least a portion of the piezoelectric layer, and a passivation layer disposed on at least a portion of the upper electrode, wherein portions of the lower electrode, the piezoelectric layer, and the upper electrode overlap to form an active region of the bulk acoustic wave resonator, the method comprising:

• disposing a trimming mask on the bulk acoustic wave resonator so that
• there is no gap between the trimming mask and any portion of the bulk acoustic wave resonator on which the trimming mask is disposed,
• the trimming mask covers a first portion of the passivation layer disposed in a first region of the bulk acoustic wave resonator in which a trimming operation is not to be performed on the passivation layer, and
• the trimming mask does not cover a second portion of the passivation layer in a second region of the bulk acoustic wave resonator in which the trimming operation is to be performed on the passivation layer;
• trimming only the second portion of the passivation layer using the trimming mask;
• and
• removing the trimming mask.