Maxim Integrated Products, Inc.

Triquint Semiconductor Corporation

Ralph N Wall

Guillaume Bouche

Edward Martin Godshalk

Rick D Lutz

Haim Ben Hamou

Uppili Sridhar

Masud Hannan

Alexander Kalnitsky

Karl M Robinson

Robert F Scheer

Viktor Zekeriya

Garth G Sundberg

Jonathan Herman

Glenn Nobinger

Joseph Paul Elull

A bulk acoustic wave (BAW) resonator is constructed to reduce phase and amplitude ripples in a frequency response. The BAW resonator is fabricated on a substrate 400 &#x3bc;m thick or less, preferably approximately 325 &#x3bc;m, having a first side and a polished second side with a peak-to-peak roughness of approximately 1000 A. A Bragg mirror having alternate layers of a high acoustic impedance material, such as tungsten, and a low acoustic impedance material is fabricated on the first side of the substrate. A BAW resonator is fabricated on the Bragg mirror. A lossy material, such as epoxy, coats the second side of the substrate opposite the first side. The lossy material has an acoustic impedance in the range of 0.01&#xd7; to 1.0&#xd7; the acoustic impedance of the layers of high acoustic impedance material.

Optimal acoustic impedance materials for polished substrate coating to suppress passband ripple in BAW resonators and filters

A method of fabricating a piezoelectric resonator includes providing a bottom electrode and a piezoelectric layer coupled to the bottom electrode. A bottom metal layer of a top electrode is deposited on the piezoelectric layer. A top metal layer of the top electrode is deposited on the bottom metal layer. A photoresist layer is deposited on the top metal layer. The photoresist layer is patterned and etched. The top metal layer is patterned and etched while the etched photoresist layer remains. The bottom metal layer is patterned and etched such that an entire perimeter side surface of the top metal layer is recessed relative to a perimeter edge of the bottom metal layer. The etched photoresist layer is removed. A passivation layer is deposited on the top and bottom metal layers such that the top and bottom metal layers are isolated from a subsequent metal etch step.

Method to control BAW resonator top electrode edge during patterning

Methods of reducing phase and amplitude ripples in a BAW resonator frequency response by providing a substrate, fabricating a Bragg mirror having alternate layers of a high acoustic material and a low acoustic material on a first surface of the substrate, fabricating a BAW on the Bragg mirror, and coating a second side of the substrate opposite the first side with a lossy material having an acoustic impedance in the range of 0.01&#xd7; to 1.0&#xd7; the acoustic impedance of the layers of high impedance material, the second surface of the substrate being a polished surface. Various embodiments are disclosed.

A piezoelectric layer is coupled to a bottom electrode in a method of fabricating a piezoelectric resonator. A bottom metal layer of a top electrode is deposited on the piezoelectric layer. The bottom metal layer is patterned and etched. A top metal layer of the top electrode is deposited on the etched bottom metal layer. The top metal layer is patterned and etched. An interconnect metal layer is deposited on the etched top metal layer and the piezoelectric layer such that the interconnect metal layer isolates the bottom metal layer from subsequent etch steps.

Process of making a BAW resonator bi-layer top electrode

In accordance with the present invention, accurate and easily controlled sloped walls may be formed using AlN and preferably a heated TMAH for such purpose as the fabrication of MEMS devices, wafer level packaging and fabrication of fluidic devices. Various embodiments are disclosed.

Orientation-dependent etching of deposited AlN for structural use and sacrificial layers in MEMS

A piezoelectric resonator includes a multi-layer top electrode configured such that a top most layer protects the underlying layers from subsequent etching, thereby preventing etch undercut of the top-most layer. In one embodiment, the multi-layer top electrode is configured as a bi-layer, so that the upper layer of the bi-layer stack protects all sides of the underlying layer from subsequent etch process steps. In an alternative embodiment, at least the perimeter of a multi-layer top electrode is completely covered with overlapping interconnect metal.

BAW resonator bi-layer top electrode with zero etch undercut

A piezoelectric resonator include a multi-layer top electrode. The multi-layer top electrode includes at least a top metal layer and a bottom metal layer. A top metal layer edge is recessed compared to a bottom metal layer edge allowing conformal deposition of a passivation layer. The passivation layer covers and protects the underlying layers from subsequent etching, thereby preventing etch undercut of the top electrode. In some embodiments, the multi-layer top electrode is configured as a bi-layer. In other embodiments, an extra layer is configured between the top metal layer and the bottom metal layer, for example a shunt load layer.

A method of fabricating a BAW piezoelectric resonator, the method comprising the steps of providing a bottom electrode and a piezoelectric layer coupled to the bottom electrode. A bottom metal layer is deposited on a top electrode on the piezoelectric layer. The bottom metal layer is patterned and etched. A top metal layer of the top electrode is deposited on the etched bottom metal layer. The top metal layer is patterned and layered such that the top metal layer completely covers the top and sides of the bottom metal layer.

Methods of contacting the top layer in a BAW device by depositing a metal layer over the BAW device, patterning the metal layer so that the metal layer extends over and contacts the top electrode layer of the BAW device only at a plurality of spaced apart locations adjacent the periphery of the active resonator area, and has a common region laterally displaced from the top and bottom electrodes and electrically interconnecting the parts of the metal layer extending over and contacting the top electrode of the BAW device at the plurality of spaced apart locations.

Methods of contacting the top layer of a BAW resonator

A device and a method of forming the device are disclosed. The device includes a reflector, a first dielectric layer disposed on the reflector, and a thin film resistor disposed on the reflector. The reflector acts as a barrier between the thin film resistor and an underlying dielectric layer which may have a non-uniform thickness. Thus, the thickness control and uniformity of the dielectric layer underlying the reflector does not affect the laser trimming of the thin film resistor. In addition to serving as a barrier, the reflector reflects the trimming laser energy back towards the thin film resistor, thereby improving the efficiency of the laser trimming of the thin film resistor. Furthermore, the thickness of the first dielectric layer situated below the thin film resistor and above the reflector can be easily controlled to substantially optimize the laser trimming efficiency of the thin film resistor.

Metal trim mirror for optimized thin film resistor laser trimming

A method for forming multiple resistors on a substrate. The method initially includes providing a first resistor on the substrate. A first dielectric layer is deposited, patterned, and selectively etched over the first resistor. Second resistor material is provided over the first dielectric layer. Furthermore, landing pad material is provided over the second resistor material. The landing pad material and the second resistor material are then selectively etched. The selective etching forms contacts for the first resistor in a first region, and forms a second resistor and associated contacts in a second region.

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Beaverton, OR, United States of America

Ralph N Wall