Method for forming a multi-frequency surface acoustic wave device
View Patent ↗Provided is a method of manufacturing a multi-frequency surface acoustic wave (SAW) device on a common piezoelectric substrate. The method features varying the resonant frequency of waveguide elements of the SAW device using a single etch step. The etch step removes a sub-portion of multiple layers of conductive film disposed on the substrate.
1. A method of manufacturing a surface acoustic wave integrated circuit on a piezoelectric substrate, the method comprising:
removing a sub-portion from an upper conductive layer of a stacked conductive layer, wherein the stacked conductive layer is formed within gaps in a patterned resist layer deposited on top of the piezoelectric substrate, wherein the stacked conductive layer further includes a lower conductive layer, and wherein said removing forms both a single layer region and a multilayer region; and
forming a plurality of waveguide elements from the stacked conductive layer by lifting off all material present on the piezoelectric substrate except material associated with the single layer region and the multilayer region.
2. The method of claim 1 , wherein said forming the lower and upper conductive layers further comprises:
depositing an adhesion film adjacent to the patterned resist layer and to portions of the piezoelectric substrate exposed by the gaps;
depositing a first conductive film adjacent to the adhesion film; and
depositing, on top of the first conductive film, a second conductive film.
3. The method of claim 1 , wherein said forming the lower and upper conductive layers further comprises:
depositing an adhesion film adjacent to the patterned resist layer and to portions of the piezoelectric substrate exposed by the gaps;
depositing a first conductive film adjacent to the adhesion film;
depositing, on top of the first conductive film, a cap layer; and
depositing, on top of the cap layer, a second conductive film.
4. The method of claim 1 , wherein:
the lower and upper conductive layers comprise materials selected from the group consisting of titanium, aluminum, nickel, tungsten, and copper; and
the piezoelectric substrate comprises compounds selected from the group of compounds consisting of LiTaO 3 , LiNbO 3 , Li 2 B 4 O 7 , La 3 Ga 5 SiO 14 , and Pb(Zr x Ti 1-x )O 3 .
5. The method of claim 1 , further comprising forming the piezoelectric substrate by forming a piezoelectric layer on top of a semiconductor wafer, wherein the piezoelectric layer includes material selected from the group of materials consisting of a piezoelectric single crystal and a piezoelectric ceramic.
6. The method of claim 1 , further comprising patterning a resist material on top of the stacked conductive layer.
7. The method of claim 6 , wherein said patterning further comprises:
depositing an additional resist layer on top of the stacked conductive layer; and
removing a portion of the additional resist layer, wherein the removed sub-portion is in superimposition with the removed sub-portion from the upper conductive layer.
8. The method of claim 1 , wherein:
the plurality of waveguide elements each have an associated resonant frequency property; and
the resonant frequency properties associated with the waveguide elements in the single layer region differ from the resonant frequency properties associated with the waveguide elements in the multilayer region.