Method and system for wafer-level tuning of bulk acoustic wave resonators and filters
AssigneeNokia Mobile Phones Ltd.
InventorsJuha Ellä, Pasi Tikka, Jyrki Kaitila
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Abstract
A method and system for tuning a bulk acoustic wave device at the wafer level by adjusting the thickness of the device. In particular, the thickness of the device has a non-uniformity profile across the device surface. A mask having a thickness non-uniformity profile based partly on the thickness non-uniformity profile of the device surface is provided on the device surface for etching. A dry etching method is used to remove part of the mask to expose the underlying device surface and further removed the exposed device surface until the thickness non-uniformity of the device surface falls within tolerance of the device.
Claims27
A method of tuning a bulk acoustic wave device comprising a substrate and a plurality of acoustic wave generating and controlling layers formed on the substrate, wherein the device has a top surface layer made of a surface material and a thickness with a thickness non-uniformity profile across the top surface layer, and wherein the device has an operating frequency which varies partly with the thickness of the top surface layer, and the operating frequency can be adjusted by adjusting the thickness of the top surface layer, said method comprising the steps of:
- providing, on top of the top surface layer, a mask made of a mask material having a further non-uniformity profile partly based on the thickness non-uniformity profile of the top surface layer;
- providing an etching agent over the mask for removing the mask material from at least one mask area to expose a corresponding surface area of the top surface layer to the etching agent;
- and
- removing part of surface material from the top surface layer at the exposed surface area until a desired thickness of the top surface layer is reached, while simultaneously removing the mask material to modify the exposed surface area.
A system for tuning a bulk acoustic wave device comprising a substrate and a plurality of acoustic wave generating and controlling layers formed on the substrate, wherein the device has a top surface layer made of a surface material and a thickness with a thickness non-uniformity profile across the top surface layer, and wherein the bulk acoustic wave device has an operating frequency, which varies partly with a thickness of the top surface layer, and the operating frequency can be adjusted by adjusting the thickness of the top surface layer through a mask made of a mask material provided on top of the top surface layer, the system comprises:
- means, positioned above the device, for removing the mask material for providing a further non-uniformity profile of the mask, partly based on the thickness non-uniformity of the top surface layer;
- and
- means, positioned above the mask, for providing an etching agent over the mask for removing the mask material from at least one mask area to expose a corresponding surface area of the top surface layer to the etching agent, and for removing part of the surface material from the top surface layer at the exposed surface area until a desired thickness of the top surface layer is reached, while simultaneously removing the mask material to modify the exposed surface area.
Dependencies are inferred from the claim text.