Bulk acoustic wave (BAW) device having roughened bottom side
A bulk acoustic wave (BAW) resonator includes a substrate having a top side surface and a bottom side surface. A Bragg mirror is on the top side surface of the substrate. A bottom electrode layer is on the Bragg mirror, and a piezoelectric layer is on the bottom electrode layer. A top dielectric layer is on the piezoelectric layer, and a top electrode layer is on the top dielectric layer. The bottom side surface of the substrate has a surface roughness of at least 1 μm root mean square (RMS).
1. A method of fabricating a bulk acoustic wave (BAW) resonator, comprising:
providing a Bragg mirror on a top side surface of a substrate having a bottom side surface opposite said top side surface;
forming a bottom electrode layer on said Bragg mirror;
forming a piezoelectric layer on said bottom electrode layer;
forming a top dielectric layer on said piezoelectric layer;
forming a top electrode layer on said top dielectric layer;
roughening said bottom side surface to provide a final surface roughness of at least 1 μm root mean square (RMS); and
preserving said roughened bottom side surface from being polished.
2. A bulk acoustic wave (BAW) resonator, comprising:
a substrate having a top side surface and a bottom side surface;
a Bragg mirror on said top side surface of said substrate;
a bottom electrode layer on said Bragg mirror;
a piezoelectric layer on said bottom electrode layer;
a top dielectric layer on said piezoelectric layer, and
a top electrode layer on said top dielectric layer,
wherein said bottom side surface has a surface roughness of at least 1 μm root mean square (RMS).
3. An oscillator, comprising:
a bulk acoustic wave (BAW) resonator, comprising:
a substrate having a top side surface and a bottom side surface;
a Bragg mirror on said top side surface of said substrate;
a bottom electrode layer on said Bragg mirror;
a piezoelectric layer on said bottom electrode layer;
a top dielectric layer on said piezoelectric layer, and
a top electrode layer on said top dielectric layer,
wherein said bottom side surface has a surface roughness of at least 1 μm root mean square (RMS), and
an oscillator core coupled to said top electrode layer and to said bottom electrode layer to provide a signal input to said oscillator core.