Low voltage, low power mems transducer with direct interconnect capability

Abstract

A transceiver includes an array of pMUT elements, where each pMUT element includes: a substrate; a membrane suspending from the substrate; a bottom electrode disposed on the membrane; a piezoelectric layer disposed on the bottom electrode; and a first electrode disposed on the piezoelectric layer. Each pMUT element exhibits one or more modes of vibration.

What is claimed is: 
     
         1 . A transceiver, comprising:
 an array of elements, wherein each element is formed on;
 a substrate: 
 a membrane suspending from the substrate; 
 a bottom electrode disposed on the membrane; 
 a piezoelectric layer disposed on the bottom electrode; and 
 a first electrode disposed on the piezoelectric layer, 
   wherein each element exhibits a plurality of modes of vibration.   
     
     
         2 . The transceiver of  claim 1 , further comprising:
 a circuit for generating a signal pulse that has rising and falling edges and the rising and falling edges are symmetrical to each other, with the high and low portions of the waveform substantially equal; and   a conductor electrically coupled to the circuit and the bottom electrode so that the signal pulse is transmitted to the bottom electrode through the conductor.   
     
     
         3 . The transceiver of  claim 2 , wherein a peak-to-peak amplitude of the signal pulse connected to one of the electrodes of each piezoelectric element is less than 11 V. 
     
     
         4 . The transceiver of  claim 3 , where the other one of the electrodes of each piezoelectric element is connected to a DC bias voltage. 
     
     
         5 . The transceiver of  claim 4 , wherein the signal pulse includes at least one of a unipolar signal transitioning between two levels and a three level signal, wherein the signal pulse is the output of transmit drivers connected to the pixel array. 
     
     
         6 . The transceiver of  claim 5 , wherein a transmit drive waveform is a coded signal and includes one of a chirp and Golay code. 
     
     
         7 . The transceiver of  claim 6 , wherein the transceiver uses a coded signal for transmitting an ultrasound signal towards an organ being imaged and the received signal is processed with matched filters. 
     
     
         8 . The transceiver of  claim 6 , wherein for imaging of organs deep inside a tissue, the transceiver allows more energy to be coupled into the tissue without degrading axial resolution. 
     
     
         9 . The transceiver of  claim 1 , wherein the piezoelectric layer includes at least one of PZT, KNN, PZT-N, PMT-Pt, AIN, Sc-AIN, ZnO, PVDF and LiNiO 3 . 
     
     
         10 . The transceiver of  claim 1 , wherein the bottom electrode is electrically connected to a signal conductor made of metal and the metal is deposited on a TiO2 layer deposited on the substrate. 
     
     
         11 . The transceiver of  claim 1 , wherein a thickness of the piezoelectric layer is 2 μm or less. 
     
     
         12 . The transceiver of  claim 1 , wherein a piezoelectric element comprises a common bottom electrode and two top electrodes, a first conductor connecting all bottom electrodes of the piezo array, a column of piezo elements with first top plates connected with a second conductor and connecting to a receive amplifier, wherein the second top electrode of all piezoelectric elements in a same column are connected using a third conductor, wherein the third conductor connects to a switch that connects the second top electrode of a column to a transmit driver in transmit mode and a receive amplifier in receive mode, wherein the imaging device has one or more columns. 
     
     
         13 . The transceiver of  claim 12 , wherein a sub piezoelectric element comprising bottom and first top electrodes is polarized in the opposite direction of sub piezoelectric element consisting of the bottom electrode and the second top electrode. 
     
     
         14 . The transceiver of  claim 12 , wherein the at least one circuit is configured to send a transmit signal to the second top electrode of a piezoelectric element and, at the same time, receive a signal from the first top electrode of the piezoelectric element. 
     
     
         15 . The transceiver of  claim 12 , wherein the device is configured to perform one of continuous Doppler imaging and B mode imaging. 
     
     
         16 . The transceiver of  claim 1 , wherein lower power operation is achieved by using lower AC drive voltages in transmit mode, wherein lower transmit voltages are less than 11V AC. 
     
     
         17 . The transceiver of  claim 1 , wherein for a given electric field across the piezoelectric layer, a thickness of piezoelectric layer is made thinner to operate with lower voltages across the top and bottom electrodes, wherein the piezoelectric layer thickness is 2 μm or smaller. 
     
     
         18 . The transceiver of  claim 1 , wherein the transceiver operates in a flexural mode of operation and the elements undergo a flexural mode resonance, causing a flex tensional motion of the membrane to transmit acoustic signals, wherein a received pressure signal from an object being imaged is converted to electrical charge by a flexural mode resonance of an element. 
     
     
         19 . An imaging device, comprising:
 a transceiver substrate including:
 a substrate; 
 at least one membrane disposed on the substrate; and 
 a plurality of piezoelectric elements disposed on the at least one membrane, each of the plurality of piezoelectric elements including;
 a bottom electrode; 
 a piezoelectric layer disposed on the bottom electrode; 
 first top electrodes disposed on the piezoelectric layer, where each element exhibits one of more modes of vibration and 
 
   an ASIC chip electrically coupled to the transceiver substrate by a three dimensional interconnection mechanism and including:
 at least one circuit for controlling one or more of the plurality of piezoelectric elements; and 
 a control unit electrically coupled to the at least one circuit and controlling the at least one circuit. 
   
     
     
         20 . The imaging device of  claim 19 , wherein the bottom electrode is a signal electrode and wherein the first top electrode is connected to one of a ground or a DC bias, wherein all top electrodes in the plurality of piezoelectric elements are connected together using conductors. 
     
     
         21 . The imaging device of  claim 19 , wherein the at least one circuit includes:
 a transmit driver for sending a transmit signal to the bottom electrode; and   an amplifier for receiving a receive signal from the bottom electrode and amplifying the receive signal.   
     
     
         22 . The imaging device of  claim 21 , wherein the at least one circuit includes:
 a switch having a first terminal electrically coupled to the bottom electrode and a second terminal toggling between two conductors that are coupled to the transmit driver and the amplifier.   
     
     
         23 . The imaging device of  claim 22 , wherein the second terminal of the switch toggles to the conductor coupled to the amplifier during a receive mode so that an electrical charge developed on the bottom electrode is transferred to the amplifier. 
     
     
         24 . The imaging device of  claim 19 , wherein the transmit signal is a pulse wave modulated (PWM) signal. 
     
     
         25 . The imaging device of  claim 24 , wherein the plurality of piezoelectric elements are further arranged into columns, wherein a width of the PWM signal used to drive different columns of piezoelectric elements is adjusted to implement a transmit apodization. 
     
     
         26 . The imaging device of  claim 24 , wherein the transmit signal uses a PWM signal width to modulated power transmitted from the transducer. 
     
     
         27 . The imaging device of  claim 19 , wherein the transmit signal has two or more levels and a number of the levels is used to modulate a power of the transmitted ultrasound signal from the transducer. 
     
     
         28 . The imaging device of  claim 19 , wherein the at least one membrane is preconfigured to boost membrane pressure output. 
     
     
         29 . The imaging device of  claim 19 , wherein the imaging device is an ultrasonic medical probe. 
     
     
         30 . The imaging device of  claim 19 , further comprising a rechargeable battery. 
     
     
         31 . The imaging device of  claim 19 , wherein the plurality of piezoelectric elements are arranged in an array and wherein a piezoelectric element comprising a common bottom electrode and two top electrodes, a first conductor connecting all bottom electrodes of the array, a row of piezoelectric elements with first top plates connected with a second conductor and connecting to a receive amplifier, wherein the second top electrode of all piezoelectric elements in a same column are connected using a third conductor, wherein the third conductor connects to a switch that connects the second top electrode of a column to transmit driver in transmit mode and a receive amplifier in receive mode, wherein the imaging device has one or more columns and one or more rows of piezoelectric elements in the array. 
     
     
         32 . The imaging device of  claim 31 , wherein the imaging device is used to perform biplane imaging. 
     
     
         33 . The imaging device of  claim 31 , wherein variable weighting is applied to each column of the array and is used to modulated output power levels, wherein Doppler and B Mode imaging share a same power supply. 
     
     
         34 . The imaging device of  claim 33 , wherein the variable weighting is achieved using PWM signaling. 
     
     
         35 . The imaging device of  claim 34 , wherein the variable weighting is achieved by electronically changing a height of a column.