US-12620962-B2 - Surface acoustic wave sensor assembly

US12620962B2US 12620962 B2US12620962 B2US 12620962B2US-12620962-B2

Abstract

A method for fabricating a sensor device that includes an integrated sensor assembly having a surface acoustic wave (SAW) sensor disposed on a piezoelectric substrate. The SAW sensor is adapted to measure an environmental condition of an environment in response to an RF signal. The SAW sensor includes an interdigitated transducer (IDT) formed on a substrate having at least a layer of a piezoelectric material. The SAW sensor includes either one or more SAW reflectors of a second IDT formed on the piezoelectric material. The SAW sensor further includes an RF antenna, a matching circuit and a waveguide are formed on the piezoelectric material. The SAW sensor and the RF antenna are integrated with one another on the piezoelectric material.

Inventors

Chuang-Chia Lin

Assignees

APPLIED MATERIALS, INC.

Dates

Publication Date: 20260505
Application Date: 20240112

Claims (17)

1 . A method for fabricating a sensor device, comprising: fabricating a first integrated sensor assembly by: depositing a first conductive structure onto a piezoelectric substrate, the first conductive structure forming a radio frequency (RF) antenna, depositing a second conductive structure onto the piezoelectric substrate, the second conductive structure forming matching circuitry coupled to the RF antenna, depositing a third conductive structure onto the piezoelectric substrate, the third conductive structure forming a first interdigitated transducer (IDT) coupled to the RF antenna, wherein the first IDT is a component of a first surface acoustic wave (SAW) sensor, depositing a fourth conductive structure onto the piezoelectric substrate, the fourth conductive structure forming a second IDT, and depositing a fifth conductive structure onto the piezoelectric substrate, the fifth conductive structure forming one or more waveguides disposed between the first IDT and the second IDT, the one or more waveguides comprising one or more planar conductors formed on a surface of the piezoelectric substrate and patterned to define an acoustic propagation path that maintains a SAW propagating between the first IDT and the second IDT.
2 . The method of claim 1 , wherein the first conductive structure, the second conductive structure, the third conductive structure, the fourth conductive structure, and the fifth conductive structure form a single conducting layer, and wherein the depositing of the first conductive structure, the second conductive structure, the third conductive structure, the fourth conductive structure, and the fifth conductive structure is performed together.
3 . The method of claim 1 , wherein the RF antenna, the matching circuitry, the first IDT, and the second IDT each comprise one or more planar conductors.
4 . The method of claim 1 , further comprising depositing a protective coating on at least one of the first conductive structure or the second conductive structure.
5 . The method of claim 1 , wherein the first IDT comprises a first arrangement of digits, the first arrangement of digits adapting the first IDT to operate in a first frequency range.
6 . The method of claim 5 , wherein the first IDT and the second IDT are disposed on the piezoelectric substrate such that a gap of a size corresponding to an integer multiple of a quarter wavelength of a wave having a frequency within the first frequency range is between the first IDT and the second IDT.
7 . The method of claim 1 , further comprising fabricating a second integrated sensor assembly by depositing a second SAW sensor onto the piezoelectric substrate, wherein the second IDT is a component of the second SAW sensor.
8 . The method of claim 7 , wherein depositing the second SAW sensor comprises: depositing at least one of (a) one or more SAW reflectors communicatively coupled to the second IDT, or (b) a sixth conductive structure forming a third IDT.
9 . The method of claim 8 , further comprising depositing a seventh conductive structure on the piezoelectric substrate, the seventh conductive structure forming a second RF antenna coupled to the second IDT.
10 . The method of claim 8 , wherein the first IDT comprises a first arrangement of digits, wherein the first arrangement of digits adapts the first IDT to operate in a first frequency range, and wherein the second IDT comprises a second arrangement of digits, wherein the second arrangement of digits adapts the second IDT to operate in a second frequency range.
11 . The method of claim 8 , wherein the second SAW sensor comprises a SAW reflector, and wherein the first IDT and the SAW reflector are disposed such that a gap of a size corresponding to an integer multiple of a quarter wavelength of a SAW having a frequency within a third frequency range associated with an arrangement of digits of the second IDT is between the second IDT and the SAW reflector.
12 . The method of claim 1 , wherein depositing the first conductive structure comprises: depositing a photoresist material on the piezoelectric substrate; performing a patterning operation to cure a selected portion of the photoresist material; performing an etch operation to remove either the selected portion or another portion of the photoresist material; depositing a conductive material on the photoresist material; and performing a selective etch process to remove a remaining portion of the photoresist material and the conductive material deposited on the remaining portion of the photoresist material.
13 . The method of claim 1 , further comprising disposing a protective coating or cover over the first conductive structure.
14 . A method for fabricating a sensor device, comprising: fabricating a first surface acoustic wave (SAW) sensor on a piezoelectric substrate by: depositing a first conductive structure onto the piezoelectric substrate, the first conductive structure forming a first interdigitated transducer (IDT), the first IDT having a first arrangement of digits to generate a first SAW responsive to receiving a first radio frequency (RF) signal in a first frequency range, and depositing a second conductive structure onto the piezoelectric substrate, the second conductive structure forming matching circuitry coupled to a first RF antenna communicatively coupled to the first IDT; and fabricating a second SAW sensor on the piezoelectric substrate by: depositing a third conductive structure onto the piezoelectric substrate, the third conductive structure forming a second IDT, the second IDT having a second arrangement of digits, depositing a fourth conductive structure onto the piezoelectric substrate, the fourth conductive structure forming a second RF antenna communicatively coupled to the second IDT, and depositing a fifth conductive structure onto the piezoelectric substrate, the fifth conductive structure forming one or more waveguides disposed between the first IDT and the second IDT, the one or more waveguides comprising one or more planar conductors formed on a surface of the piezoelectric substrate and patterned to define an acoustic propagation path that maintains a SAW propagating between the first IDT and the second IDT.
15 . The method of claim 14 , wherein depositing the first conductive structure comprises: depositing a photoresist material on the piezoelectric substrate; performing a patterning operation to cure a selected portion of the photoresist material; performing an etch operation to remove either the selected portion or another portion of the photoresist material; depositing a metal material on the photoresist material; and performing a selective etch process to remove a remaining portion of the photoresist material and the metal deposited on the remaining portion of the photoresist material.
16 . The method of claim 14 , further comprising depositing a sixth conductive structure onto the piezoelectric substrate, the sixth conductive structure forming one or more SAW reflectors communicatively coupled to at least one of the first IDT or the second IDT.
17 . The method of claim 14 , wherein the first SAW sensor is disposed on a first surface of the piezoelectric substrate, wherein the second SAW sensor is disposed on a second surface of the piezoelectric substrate, different than the first surface, and wherein the one or more waveguides are disposed on the first surface.

Description

RELATED APPLICATIONS The present application is a divisional of application Ser. No. 17/068,725, filed Oct. 12, 2020, the contents of which are incorporated by reference herein. TECHNICAL FIELD Some embodiments of the present disclosure relate, in general, to a sensor device having a surface acoustic wave (SAW) sensor assembly to measure an environmental condition of an environment. BACKGROUND Surface acoustic waves (SAWs) are sound waves that travel parallel to the surface of an elastic material. The general mathematical discussion of SAW was first reported by Lord Rayleigh in 1855, but the application in electronic devices was not exploited until 1965 by White and Voltmer utilizing interdigital transducer on piezoelectric materials. SAWs are used in an electronic devices, particularly RF/IF filters. The transduction from electrical energy to mechanical energy (in the form of SAWs) is accomplished through the use of piezoelectric materials. Piezoelectric materials are materials that have the ability to generate internal electrical charge from mechanical stress as well as internally generate mechanical strain in response to an applied electric field. A SAW transducer is often used on a surface of piezoelectric materials to convert electrical energy to mechanical energy (e.g., SAWs) as well as convert SAWs into electrical energy. SAW devices may use SAWs in electronic components to provide a number of different functions, including delay lines, filters, resonators, correlators, converters, sensors, and the like. SAW devices can be disposed on wafers to perform their respective functions. SUMMARY Some embodiments described herein cover a sensor device including an integrated sensor assembly having a surface acoustic wave (SAW) sensor disposed on a substrate having at least a layer of a piezoelectric material. The SAW sensor may be adapted to measure an environmental condition based on detection of SAW properties responsive to receiving an incoming radio frequency (RF) signal. The SAW sensor may include an interdigitated transducer (IDT) formed on the piezoelectric material. The IDT may generate a SAW based on the environmental condition responsive to receiving the incoming RF signal. The SAW sensor may include one or more SAW reflectors that communicates with the IDT. The SAW sensor may include another IDT to receive the SAW wave and generate an outgoing RF signal. The SAW sensor assembly may further include an RF antenna and matching circuitry. The matching circuitry may be connected to the RF antenna and the IDT. The SAW sensor, the RF antenna, and the matching circuitry may be integrated with each other on the piezoelectric material. In further embodiments, the sensor assembly may include a second IDT that receives the SAW from the first IDT and generates an oscillating potential associated with an acoustic frequency of the received SAW. This oscillating potential may include information associated with a measured environmental condition across a region of the surface of the piezoelectric substrate or piezoelectric layer. The sensor assembly may include a second RF antenna and second matching circuitry to output an outgoing RF signal associated with the oscillating potential. In example embodiments, a method is disclosed for fabricating a sensor device. The method may include fabricating an integrated sensor assembly by depositing a first conductive structure onto a substrate having at least a layer of a piezoelectric material, where the first conductive structure forms a radio frequency (RF) antenna. The method may further include depositing a second conductive structure onto the piezoelectric material, where the second conductive structure forms matching circuitry that is connected to the RF antenna. The method may further include depositing a third conductive structure onto the piezoelectric material, where the third conductive structure forms an interdigitated transducer (IDT) connected to the RF antenna, wherein the IDT is a component of a surface acoustic wave (SAW) sensor. The method may further include depositing a fourth conductive structure onto the piezoelectric material, where the fourth conductive structure forms at least one of a) one or more SAW reflectors or b) a second IDT. The first conductive structure, second conductive structure, third conductive structure and/or fourth conductive structure may be formed together in a single deposition operation in some embodiments. In some embodiments, the sensor assembly may include a SAW sensor adapted to measure an environmental condition responsive to receiving an incoming RF signal. The SAW sensor may include at least a layer of a piezoelectric material disposed on a base substrate. The SAW sensor may further include a first IDT formed on the piezoelectric substrate, where the first IDT operates at a base resonant frequency. The SAW sensor may include a dielectric coating with a thickness or material associated with a shift in the base resonant f