The present disclosure relates to sensors and, more specifically, to biosensors.
Various types of biosensors exist, and one type of particular interest are radio-frequency (RF), microwave (MW), millimeter wave (mmW) and terahertz (THz) biosensors (all of which are referred to herein as biosensors for simplicity of discussion). Such biosensors treat biological tissue as a dielectric substance having a unique dielectric signature, which can be characterized by frequency dependent parameters such as permittivity and conductivity, and can operate on the principle of resonator-based biosensors. With biosensors, capacitive sensing is sometimes employed where changes in permittivity are reflected as changes in capacitance, through components like interdigitated electrodes, resonators and microstrip structures.
Such biosensors can subject biomatter to electro-mechanical (EM) waves and this allows biosensors to observe the unique permittivity signatures of the biomatter without having to directly contact the fluid under test. Permittivity (in the framework of electromagnetics) is a fundamental material property that describes how a material will affect, and be affected by, a time-varying electromagnetic field.
According to one embodiment herein, a structure includes a first layer, where the first layer includes a recess. The structure further includes an intermediate layer contacting the first layer and a contact-free biosensor aligned above the recess. A portion of the intermediate layer is positioned along the recess, and the portion of the intermediate layer that is positioned along the recess separates the contact-free biosensor from the recess.
According to another embodiment herein, a structure includes a first layer, where the first layer includes a recess. The structure further includes an intermediate layer contacting the first layer and a plurality of contact-free biosensors aligned above the recess. A portion of the intermediate layer is positioned along the recess and the portion of the intermediate layer that is positioned along the recess separates the contact-free biosensors from the recess.
According to a further embodiment herein a method forms a first layer to include a recess, forms an intermediate layer to contact the first layer, and forms a contact-free biosensor aligned above the recess. A portion of the intermediate layer is formed to be positioned along the recess, and the portion of the intermediate layer that is positioned along the recess is formed to separate the contact-free biosensor from the recess.
The embodiments herein will be better understood from the following detailed description with reference to the drawings, which are not necessarily drawn to scale and in which:
Bio-sensing of liquids with clear identification is a major issue for lab-on-a-chip solutions. As noted above, with biosensors, capacitive sensing is sometimes employed where changes in permittivity are reflected as changes in capacitance, through components like interdigitated electrodes, resonators and microstrip structures. For example, with some biosensors the radio-frequency (RF) spectrum of the droplet deposited on the transmission line is detected. Others can use optical detection and electrical detection.
Contact-free biosensors herein can be radio-frequency (RF), microwave (MW), millimeter wave (mmW) and terahertz (THz) microfluidic biosensors and can subject biomatter to electro-mechanical (EM) waves and this allows such contact-free biosensors to observe the unique permittivity signatures of the biomatter. Permittivity (in the framework of electromagnetics) is a fundamental material property that describes how a material will affect, and be affected by, a time-varying electromagnetic field.
The devices and methods herein perform time-varying electromagnetic field sensing to obtain a permittivity signature of molecular species by supplying the bio-liquid via microfluidic channels created in a silicon substrate. Specifically, with the devices and methods herein, transistors or passive devices (e.g., antenna, transmission line, etc.) are located in close vicinity of a microfluidic channel to obtain the signature of molecular species without direct contact between the sensor and the molecular species (contact-free sensing).
A field effect transistor 100 is shown in
As shown in
All elements of the transistor 100 are formed using conventional processing, whether currently known or developed in the future. Additionally, contacts and additional wiring layers are generally formed above the transistor 100 in a multi-layer laminated structure to provide electrical contacts to the various components of the transistor 100.
Broken line box 120 in
A broken line box is also used to represent a location of conventional analysis circuitry 118 used with conventional lab-on-a-chip devices that can be formed in layers over the first layer 102. The analysis circuitry 118 is connected to the transistors 100 (in upper layers of the lab-on-a-chip device that are not shown in
The analysis circuitry 118 in combination with the transistor(s) 100 allows the lab-on-a-chip device to fully and automatically analyze, and provide reports of, the fluid within the recess 104. In operation, a fluid under test (e.g., biological fluid) is supplied to the fluid receptacle 120 of the recess 104. The fluid under test travels to fill the recess 104 (through capillary forces (capillary action), microscopic pumps (microelectronic mechanical structures (MEMS)). The one or more transistors 100 evaluate the fluid under test by transmitting and receiving a time-varying electromagnetic field to evaluate the permittivity signatures of the fluid under task.
The use of multiple transistors 100 as shown in
In some examples herein, the contact-free biosensor devices herein can be any form of passive device, such as transmission line(s), antenna(s), etc. Therefore, as shown in
As shown in
The use of multiple transmission lines or antennas 138 and/or multiple recesses 162, 164, as shown in
As shown in
More specifically, in
In
In
While
In
As shown in
The above-described structures and methods provide a location (e.g., recess(es) 104, 162, 164) for a fluid under test to be positioned within close enough proximity of an active or passive contact-free biosensor 100, 138 to allow time-varying electromagnetic field sensing, while the intermediate layer (e.g., 106 alone; 106, 132, and 134; or 142 and 134, etc.) prevents the fluid under test from coming into direct contact with the active or passive device(s) 100, 138. Therefore, these structures and methods provide a contact-free biosensor that is simply and easily formed during FEOL or BEOL processing. Specifically, FEOL and BEOL processes are mature technologies and all existing sophisticated FEOL and BEOL techniques can be utilized to inexpensively and accurately achieve the needed shape, size, etc., components to accommodate the fluid under test that will be utilized with the lab-on-a-chip device.
Further, by forming the recess 104 in the bulk substrate 102 vertical space is saved compared to devices that locate microfluid channels on tops or in the middle of lab-on-a-chip devices. Forming the recess 104 in the substrate 102 also simplifies recess 104 location and associated processing because the bulk substrate 102 typically does not contain any components and the recess(es) can be formed in any desired location while, in contrast, channels formed in upper layers of lab-on-a-chip structure must carefully avoid intersecting with other structures and must avoid damaging other structures during channel formation processes.
For purposes herein, an “insulator” is a relative term that means a material or structure that allows substantially less (<95%) electrical current to flow than does a “conductor.” The dielectrics (insulators) mentioned herein can, for example, be grown from either a dry oxygen ambient or steam and then patterned. Alternatively, the dielectrics herein may be formed (grown or deposited) from any of the many candidate low dielectric constant materials (low-K (where K corresponds to the dielectric constant of silicon dioxide) materials such as fluorine or carbon-doped silicon dioxide, porous silicon dioxide, porous carbon-doped silicon dioxide, spin-on silicon or organic polymeric dielectrics, etc.) or high dielectric constant (high-K) materials, including but not limited to silicon nitride, silicon oxynitride, a gate dielectric stack of SiO2 and Si3N4, hafnium oxide (HfO2), hafnium zirconium oxide (HfZrO2), zirconium dioxide (ZrO2), hafnium silicon oxynitride (HfSiON), hafnium aluminum oxide compounds (HfAlOx), other metal oxides like tantalum oxide, etc. The thickness of dielectrics herein may vary contingent upon the required device performance.
The conductors mentioned herein can be formed of any conductive material, such as polycrystalline silicon (polysilicon), amorphous silicon, a combination of amorphous silicon and polysilicon, and polysilicon-germanium, rendered conductive by the presence of a suitable dopant. Alternatively, the conductors herein may be one or more metals, such as tungsten, hafnium, tantalum, molybdenum, titanium, or nickel, or a metal silicide, any alloys of such metals, and may be deposited using physical vapor deposition, chemical vapor deposition, or any other technique known in the art.
There are various types of transistors, which have slight differences in how they are used in a circuit. For example, a bipolar transistor has terminals labeled base, collector, and emitter. A small current at the base terminal (that is, flowing between the base and the emitter) can control, or switch, a much larger current between the collector and emitter terminals. Another example is a field-effect transistor, which has terminals labeled gate, source, and drain. A voltage at the gate can control a current between source and drain. Within such transistors, a semiconductor (channel region) is positioned between the conductive source region and the similarly conductive drain (or conductive source/emitter regions), and when the semiconductor is in a conductive state, the semiconductor allows electrical current to flow between the source and drain, or collector and emitter. The gate is a conductive element that is electrically separated from the semiconductor by a “gate oxide” (which is an insulator); and current/voltage within the gate changes makes the channel region conductive, allowing electrical current to flow between the source and drain. Similarly, current flowing between the base and the emitter makes the semiconductor conductive, allowing current to flow between the collector and emitter.
Generally, transistor structures, in one example, can be formed by depositing or implanting impurities into a substrate to form at least one semiconductor channel region, bordered by shallow trench isolation regions below the top (upper) surface of the substrate. A “substrate” herein can be any material appropriate for the given purpose (whether now known or developed in the future) and can be, for example, silicon-based wafers (bulk materials), ceramic materials, organic materials, oxide materials, nitride materials, etc., whether doped or undoped. The “shallow trench isolation” (STI) structures are generally formed by patterning openings/trenches within the substrate and growing or filling the openings with a highly insulating material (this allows different active areas of the substrate to be electrically isolated from one another).
When patterning any material herein, the material to be patterned can be grown or deposited in any known manner and a patterning layer (such as an organic photoresist) can be formed over the material. The patterning layer (resist) can be exposed to some pattern of light radiation (e.g., patterned exposure, laser exposure, etc.) provided in a light exposure pattern, and then the resist is developed using a chemical agent. This process changes the physical characteristics of the portion of the resist that was exposed to the light. Then one portion of the resist can be rinsed off, leaving the other portion of the resist to protect the material to be patterned (which portion of the resist that is rinsed off depends upon whether the resist is a negative resist (illuminated portions remain) or positive resist (illuminated portions are rinsed off). A material removal process is then performed (e.g., wet etching, anisotropic etching (orientation dependent etching), plasma etching (reactive ion etching (RIE), etc.)) to remove the unprotected portions of the material below the resist to be patterned. The resist is subsequently removed to leave the underlying material patterned according to the light exposure pattern (or a negative image thereof).
While only one or a limited number of transistors are illustrated in the drawings, those ordinarily skilled in the art would understand that many different types transistor could be simultaneously formed with the embodiment herein and the drawings are intended to show simultaneous formation of multiple different types of transistors; however, the drawings have been simplified to only show a limited number of transistors for clarity and to allow the reader to more easily recognize the different features illustrated. This is not intended to limit this disclosure because, as would be understood by those ordinarily skilled in the art, this disclosure is applicable to structures that include many of each type of transistor shown in the drawings.
The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the foregoing. As used herein, the singular forms “a,” “an,” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. Furthermore, as used herein, terms such as “right”, “left”, “vertical”, “horizontal”, “top”, “bottom”, “upper”, “lower”, “under”, “below”, “underlying”, “over”, “overlying”, “parallel”, “perpendicular”, etc., are intended to describe relative locations as they are oriented and illustrated in the drawings (unless otherwise indicated) and terms such as “touching”, “in direct contact”, “abutting”, “directly adjacent to”, “immediately adjacent to”, etc., are intended to indicate that at least one element physically contacts another element (without other elements separating the described elements).
Each respective figure, in addition to illustrating methods of and functionality of the present embodiments at various stages, also illustrates the logic of the method as implemented, in whole or in part, by one or more devices and structures. Such devices and structures are configured to (i.e., include one or more components, such as resistors, capacitors, transistors and the like that are connected to enable the performing of a process) implement the method described above. In other words, one or more computer hardware devices can be created that are configured to implement the method and processes described herein with reference to the FIGs. and their corresponding descriptions.
Embodiments herein may be used in a variety of electronic applications, including but not limited to advanced sensors, memory/data storage, semiconductors, microprocessors and other applications. A resulting device and structure, such as an integrated circuit (IC) chip can be distributed by the fabricator in raw wafer form (that is, as a single wafer that has multiple unpackaged chips), as a bare die, or in a packaged form. In the latter case the chip is mounted in a single chip package (such as a plastic carrier, with leads that are affixed to a motherboard or other higher level carrier) or in a multichip package (such as a ceramic carrier that has either or both surface interconnections or buried interconnections). In any case the chip is then integrated with other chips, discrete circuit elements, and/or other signal processing devices as part of either (a) an intermediate product, such as a motherboard, or (b) an end product. The end product can be any product that includes integrated circuit chips, ranging from toys and other low-end applications to advanced computer products having a display, a keyboard or other input device, and a central processor.
The corresponding structures, materials, acts, and equivalents of all means or step plus function elements in the claims below are intended to include any structure, material, or act for performing the function in combination with other claimed elements as specifically claimed. The description of the present embodiments has been presented for purposes of illustration and description but is not intended to be exhaustive or limited to the embodiments in the form disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the embodiments herein. The embodiments were chosen and described in order to best explain the principles of such, and the practical application, and to enable others of ordinary skill in the art to understand the various embodiments with various modifications as are suited to the particular use contemplated.
While the foregoing has been described in detail in connection with only a limited number of embodiments, it should be readily understood that the embodiments herein are not limited to such disclosure. Rather, the elements herein can be modified to incorporate any number of variations, alterations, substitutions or equivalent arrangements not heretofore described, but which are commensurate with the spirit and scope herein. Additionally, while various embodiments have been described, it is to be understood that aspects herein may be included by only some of the described embodiments. Accordingly, the claims below are not to be seen as limited by the foregoing description. A reference to an element in the singular is not intended to mean “one and only one” unless specifically stated, but rather “one or more.” All structural and functional equivalents to the elements of the various embodiments described throughout this disclosure that are known or later, come to be known, to those of ordinary skill in the art are expressly incorporated herein by reference and intended to be encompassed by this disclosure. It is therefore to be understood that changes may be made in the particular embodiments disclosed which are within the scope of the foregoing as outlined by the appended claims.