News Column

Patent Issued for MEMS Device Fabricated with Integrated Circuit

May 28, 2014



By a News Reporter-Staff News Editor at Journal of Engineering -- According to news reporting originating from Alexandria, Virginia, by VerticalNews journalists, a patent by the inventors Udayakumar, Kezhakkedath R. (Dallas, TX); Denison, Marie (Plano, TX); Moise, Theodore S. (Dallas, TX), filed on July 19, 2013, was published online on May 13, 2014.

The assignee for this patent, patent number 8723241, is Texas Instruments Incorporated (Dallas, TX).

Reporters obtained the following quote from the background information supplied by the inventors: "This relates to the field of micro-electromechanical systems (MEMS) devices with piezoelectric elements.

"Micro-electromechanical systems (MEMS) devices may include piezoelectric elements formed by thin film processes mechanically coupled to a flexible element responsive to force imparted by a proof mass. In some versions, the piezoelectric elements may have electrodes on top and bottom surfaces and operate in the d.sub.31 mode. In other versions, the piezoelectric elements may have at least two electrodes on the top surfaces and operate in the d.sub.33 mode. Integrating the piezoelectric elements, the proof mass and the flexible element into the MEMS device may involve a trade-off between fabrication cost of the MEMS device and performance of the piezoelectric element."

In addition to obtaining background information on this patent, VerticalNews editors also obtained the inventors' summary information for this patent: "New piezoelectric element micro-electromechanical systems (MEMS) devices and methods for their fabrication are disclosed.

"In disclosed embodiments, a MEMS device is integrated on a same substrate as an integrated circuit. A ferroelectric layer is formed and patterned into a piezoelectric element over a dielectric isolation layer over circuit components formed on a substrate. Electrodes for the piezoelectric element are formed on front, back or both front and back surfaces of the piezoelectric element, and contacts are formed to establish electrical connections between the circuitry components and the piezoelectric element electrodes. The back of the substrate is etched to remove material from the substrate and define a flexible element, a proof mass and a base for vibration of the piezoelectric element.

"In one form, the piezoelectric element may be formed by applying a plurality of layers of sol gel containing piezoelectric material, such as lead zirconate titanate (PZT), or doped PZT such as lead lanthanum zirconate titanate (PLZT) or lead niobium zirconate titanate (PZNT), over a top surface of the dielectric isolation layer, so that each layer is dried before applying the subsequent layer. After the sol gel layers have been applied, the sol gel layer stack is annealed to form a ferroelectric layer with a perovskite structure. The ferroelectric layer may also be formed by other processes, for example metal organic chemical vapor deposition (MOCVD) or a physical deposition process such as sputtering.

"The ferroelectric element and electrodes may be formed to operate the MEMS device in a d.sub.31 mode, with one electrode formed on a bottom surface and another electrode formed on a top surface of the ferroelectric element; or in a d.sub.33 mode, with both electrodes formed on the same surface of the ferroelectric element. Hydrogen barrier layers may be formed over and below the piezoelectric element. Front side trenches may be formed at a periphery of the MEMS device extending down into the substrate to assist singulation. The bottom of the substrate may be etched to expose an area for the flexible element and an area corresponding to the front side trenches for singulation, and to mask an area for the proof mass. The etching removes material from the bottom in the flexible element area so as to form the flexible element at the top of the substrate, to remove material from the singulation area to assist singulation of the MEMS device from a remainder of the substrate, and to form the proof mass by leaving substrate material in the proof mass area. The piezoelectric element overlaps the flexible element so as to be vibrated."

For more information, see this patent: Udayakumar, Kezhakkedath R.; Denison, Marie; Moise, Theodore S.. MEMS Device Fabricated with Integrated Circuit. U.S. Patent Number 8723241, filed July 19, 2013, and published online on May 13, 2014. Patent URL: http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO2&Sect2=HITOFF&p=74&u=%2Fnetahtml%2FPTO%2Fsearch-bool.html&r=3695&f=G&l=50&co1=AND&d=PTXT&s1=20140513.PD.&OS=ISD/20140513&RS=ISD/20140513

Keywords for this news article include: Texas Instruments Incorporated.

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Source: Journal of Engineering


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