Method of producing a piezoelectric component
View Patent ↗A method for producing a piezoelectric component comprising at least two stacked crystal filters comprises the steps of depositing of the layer stack above the bottom electrode and the subsequent patterning of the upper electrically conductive layer and, if appropriate, second piezoelectric layers. Thus, it is possible, in a simple manner, with a minimum of process steps, to produce a piezoelectric component comprising two stacked crystal filters which are directly connected to one another via their bottom and central electrodes. The piezoelectric component furthermore has the advantage that applications in which a high stop band attenuation is important can be realized with a relatively small number of filter stages. In this case, through the use of at least two stacked crystal filters, it is possible to achieve an excellent out-of-band rejection also for “single-ended signals”.
1. A method for producing a piezoelectric component containing at least two stacked crystal filters, comprising the following steps:
a) providing a substrate;
b) producing at least one bottom electrode on the substrate from a first electrically conductive layer applied on the substrate;
c) applying a layer stack on the substrate at least in a region of the bottom electrode, in which the layer stack comprises, beginning with a bottommost layer as, a first piezoelectric layer, a second electrically conductive layer, a second piezoelectric layer and a third electrically conductive layer;
d) producing at least a first opening in the third electrically conductive layer and the second piezoelectric layer of the layer stack to provide a contact hole for the second electrically conductive layer, and producing second openings in at least the third electrically conductive layer of the layer stack in such a way that at least two stacked crystal filters are produced;
e) contact-connecting the third electrically conductive layer.
2. The method as claimed in claim 1 , wherein, before step e), a resonant frequency of at least one of the stacked crystal filters produced is measured and in a further step, a layer thickness of the third electrical conductive layer is corrected by local etching-away.
3. The method as claimed in claim 1 , wherein, before step d) andlor e), at least one upper acoustic mirror is produced.
4. The method as claimed in claim 3 , wherein the upper acoustic mirrow comprises another layer stack applied on the third electrically conductive layer, the another layer stack having at least one layer made of an electrically conductive metal.
5. The method as claimed in claim 4 , wherein the at least one layer made of the electrically conductive metal fills the contact hole.
6. The method as claimed in claim 4 , wherein all the layers of the another layer stack are electrically conductive.
7. The method as claimed in claim 6 , wherein the upper acoustic mirror comprises a layer sequence of electrically conductive metals which alternately have a high and low acoustic impedance.
8. The method as claimed in claim 1 , wherein the first and second piezoelectric layer have different layer thicknesses.
9. The method as claimed in claim 1 , wherein, before step b), a lower acoustic mirror is produced in the substrate.
10. The method as claimed in claim 9 , wherein the lower acoustic mirror comprises a lower sequence made of materials having alternately a high and a low acoustic impedance.
11. The method as claimed in claim 1 , wherein the bottom electrode, the first piezoelectric layer, a central electrode, the second piezoelectric layer and the top electrode are deposited in such a way that the layer stack formed from these layers has a layer thickness which corresponds approximately to half a wavelength of a mechanical oscillation of the stacked crystal filters.