CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a non-provisional of U.S. provisional patent application Ser. No. 62/844,000, filed May 6, 2019, the disclosure of which is hereby incorporated herein by reference in its entirety.

TECHNICAL FIELD

This disclosure generally relates to acoustic wave resonator devices, including acoustic wave sensors and fluidic devices incorporating acoustic wave resonators and related systems suitable for biosensing or biochemical sensing applications.

BACKGROUND

A biosensor (or biological sensor) is an analytical device including a biological element and a transducer that converts a biological response into an electrical signal. Certain biosensors involve a selective biochemical reaction between a specific binding material (e.g., an antibody, a receptor, a ligand, etc.) and a target species (e.g., molecule, protein, DNA, vims, bacteria, etc.), and the product of this highly specific reaction is converted into a measurable quantity by a transducer. Other sensors may utilize a nonspecific binding material capable of binding multiple types or classes of molecules or other moieties that may be present in a sample. The term “functionalization material” may be used herein to generally relate to both specific and nonspecific binding materials. Transduction methods used with biosensors may be based on various principles, such as electrochemical, optical, electrical, acoustic, etc. Among these, acoustic transduction offers a number of potential advantages, such as being real time, label-free, and low cost, as well as exhibiting high sensitivity.

An acoustic wave device employs an acoustic wave that propagates through or on the surface of a specific binding material, whereby any changes to the characteristics of the propagation path affect the velocity and/or amplitude of the wave. Acoustic wave devices are commonly fabricated by micro-electro-mechanical systems (MEMS) fabrication techniques, owing to the need to provide microscale features suitable for facilitating high-frequency operation. Presence of functionalization material on or over an active region of an acoustic wave device permits an analyte to be bound to the functionalization material, thereby altering the mass being vibrated by the acoustic wave and altering the wave propagation characteristics (e.g., velocity, thereby altering resonance frequency). Changes in velocity can be monitored by measuring the frequency, amplitude-magnitude, and/or phase characteristics of the acoustic wave device and can be correlated to a physical quantity being measured.

Typically, BAW devices are fabricated by micro-electro-mechanical systems (MEMS) fabrication techniques owing to the need to provide microscale features suitable for facilitating high frequency operation. In the context of biosensors, functionalization materials (e.g., specific binding materials; also known as bioactive probes or agents) may be deposited on sensor surfaces by various techniques, such as microarray spotting (also known as microarray printing). Functionalization materials providing non-specific binding utility (e.g., permitting binding of multiple types or species of molecules) may also be used in certain contexts, such as chemical sensing.

Existing processes for manufacturing an array of resonators includes many challenges. For example, the electrical lead lengths will increase in length as multiple rows of resonators are placed in the fluidic pathway. For example, if there are four resonators in the width of the fluidic path then the lead length to the resonators in the center of the fluidic path will be long. This in turn makes it difficult to address high density resonator sensor arrays. As an example, sensor arrays could range from 2 by 2 (4 total) to 50 by 50 (2500 total). In addition, the fluidic height of the flow channel of the sensor is directly tied to the height of the laminate board.

It may be desirable to provide a high-density BAW sensor array that provides the benefits of short electrical leads, low fluidic channel height, and high reliability by isolating the electrical connections and the fluidic interfaces on opposite sides of the BAW die. Those skilled in the art will appreciate the scope of the present disclosure and realize additional aspects thereof after reading the following detailed description in association with the accompanying drawings

SUMMARY

The techniques of this disclosure generally relate to methods of fabricating devices that include bulk acoustic wave resonator sensors that may be more effectively and easily electrically connected to a printed circuit board. The methods may include forming the bulk acoustic wave resonators on a first surface of a substrate and removing a portion of the substrate from the opposing surface of the substrate. The methods may also optionally include flip chip mounting.

Some aspects, in accordance with principles of the present disclosure, relate to methods of fabricating a bulk acoustic wave resonator structure for a fluidic device. The methods can include a first step of disposing a first conductive material over a portion of a first surface of a substrate to form at least a portion of a first electrode, the substrate having a second surface opposite the first surface. Then, a piezoelectric material may be disposed over the first electrode. Next, a second conductive material can be disposed over the piezoelectric material to form at least a portion of a second electrode. The second conductive material extends substantially parallel to the first surface of the substrate and the second conductive material at least partially extends over the first conductive material. The overlapping region of the first conductive material, the piezoelectric material, and the second conductive material form a bulk acoustic wave resonator, the bulk acoustic wave resonator having a first side and an opposing second side. An acoustic energy management structure is then disposed over a first side of the bulk acoustic wave resonator. Next a third conductive material is disposed over a portion of the second conductive material that extends beyond the bulk acoustic wave resonator, wherein the third conductive material forms an interconnect extending above the acoustic energy management structure in a direction substantially perpendicular to the first surface of the substrate. Finally a portion of the second surface of the substrate is removed to expose a chemical mechanical connection at the first electrode at a second side of the bulk wave acoustic resonator.

Other aspects, in accordance with principles of the present disclosure, relate to methods of fabricating a bulk acoustic wave resonator structure for a fluidic device. The methods can include a first step of disposing a first conductive material over a portion of a first surface of a substrate to form at least a portion of a first electrode, the substrate having a second surface opposite the first surface. Then, a piezoelectric material may be disposed over the first electrode. Next, a second conductive material can be disposed over the piezoelectric material to form at least a portion of a second electrode. The second conductive material extends substantially parallel to the first surface of the substrate and the second conductive material at least partially extends over the first conductive material. The overlapping region of the first conductive material, the piezoelectric material, and the second conductive material form a bulk acoustic wave resonator, the bulk acoustic wave resonator having a first side and an opposing second side. A reflector structure that functions as an acoustic energy management structure is then disposed over a first side of the bulk acoustic wave resonator. Next a third conductive material is disposed over a portion of the second conductive material that extends beyond the bulk acoustic wave resonator, wherein the third conductive material forms an interconnect extending above the reflector structure in a direction substantially perpendicular to the first surface of the substrate. Finally a portion of the second surface of the substrate is removed to expose a chemical mechanical connection at the first electrode at a second side of the bulk wave acoustic resonator.

Other aspects, in accordance with principles of the present disclosure, relate to methods of fabricating a bulk acoustic wave resonator structure for a fluidic device. The methods can include a first step of disposing a first conductive material over a portion of a first surface of a substrate to form at least a portion of a first electrode, the substrate having a second surface opposite the first surface. Then, a piezoelectric material may be disposed over the first electrode. Next, a second conductive material can be disposed over the piezoelectric material to form at least a portion of a second electrode. The second conductive material extends substantially parallel to the first surface of the substrate and the second conductive material at least partially extends over the first conductive material. The overlapping region of the first conductive material, the piezoelectric material, and the second conductive material form a bulk acoustic wave resonator, the bulk acoustic wave resonator having a first side and an opposing second side. An air cavity that functions as an acoustic energy management structure is then disposed over a first side of the bulk acoustic wave resonator. Next a third conductive material is disposed over a portion of the second conductive material that extends beyond the bulk acoustic wave resonator, wherein the third conductive material forms an interconnect extending above the air cavity in a direction substantially perpendicular to the first surface of the substrate. Finally a portion of the second surface of the substrate is removed to expose a chemical mechanical connection at the first electrode at a second side of the bulk wave acoustic resonator.

The details of one or more aspects of the disclosure are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the techniques described in this disclosure will be apparent from the description and drawings, and from the claims.

