Molecule detection devices and systems, and methods of fabricating them

Abstract

A device for detecting biomolecules may include a first sensor and a second sensor; an insulating material situated between the first and second sensors; a first material layer situated over the first sensor, the second sensor, and the insulating material; a second material layer situated over a portion of the first material layer, wherein the portion of the first material layer is situated over the insulating material and not over the first sensor or the second sensor, wherein a surface energy of the second material layer is different from the surface energy of the first material layer; a first lower well situated over the first sensor, the first lower well being a cavity in the insulating material, the cavity being lined by the first material layer; and a first upper well situated over the first lower well, the first upper well being a cavity in the second material layer.

Description

[0001] Attorney Docket No. ROA-1004-WO / P39519-WO

[0002] MOLECULE DETECTION DEVICES AND SYSTEMS, AND METHODS OF FABRICATING THEM

[0003] CROSS-REFERENCE TO RELATED APPLICATIONS

[0004] This application claims priority to, and hereby incorporates by reference in its entirety for all purposes, U.S. Provisional Application No. 63 / 737,055, filed December 20, 2024 and entitled “MOLECULE DETECTION DEVICES AND SYSTEMS, AND METHODS OF FABRICATING THEM.”

[0005] BACKGROUND

[0006] In recent years, magnetic nanoparticles (MNPs) have been used for molecule detection in various fields such as biosensing, environmental monitoring, and medical diagnostics. As their name suggests, MNPs possess magnetic properties, and they can be manipulated using external magnetic fields. In addition, MNPs can be functionalized with molecules to allow selective detection. For example, the surfaces of MNPs can be coated with materials such as silica, gold, or polymers to provide stability and biocompatibility, and the MNPs can be functionalized with specific ligands, antibodies, enzymes, or aptamers (single-stranded DNA or RNA molecules that bind specific targets) to target the molecule of interest. This functionalization allows the nanoparticles to selectively bind to the desired target molecule (analyte).

[0007] For detecting proteins, antibodies specific to the target protein can be conjugated to the MNP surface. For DNA detection or sequencing, MNPs conjugated with DNA probes can be used to capture specific DNA sequences from a sample, followed by detection. Magnetic immunoassays (e.g., for point-of-care diagnostics) can be used to detect proteins, pathogens, or toxins by combining MNPs functionalized with antibodies. When a sample containing the target molecules is introduced, the functionalized MNPs bind specifically to the target through molecular interactions (e.g., antigen-antibody, DNA hybridization). A magnetic field can then be applied to separate the MNP-target complexes from the rest of the sample. The presence of the target molecule after binding to MNPs can then be detected.

[0008] An advantage of MNPs is that low concentrations of target molecules can be detected due to the strong response of MNPs to external magnetic fields and ability to enrich a sample through magnetic separation. Functionalization with specific biomolecules allows selective targeting of specific analytes, reducing false positives. MNPs allow for quick and efficient separation of bound targets from complex mixtures, improving assay speed and precision. Attorney Docket No. ROA-1004-WO / P39519-WO

[0009] A variety of techniques can be used to detect the presence of the target molecule after binding to MNPs. Some of these methods use sensors to detect changes in the physical or chemical properties after binding, such as changes in magnetic properties, optical signals, or electrical signals.

[0010] It can be challenging to fabricate devices that provide consistent sensor sensitivity and, therefore, reliable detection of MNPs. Therefore, there is a need for improvements in both detection devices and methods of manufacturing them.

[0011] SUMMARY

[0012] This summary represents non-limiting embodiments of the disclosure.

[0013] In some aspects, the techniques described herein relate to a device for sensing biomolecules, the device including: a plurality of sensors, including a first sensor and a second sensor; insulating material situated between the first sensor and the second sensor; a first material layer situated over the first sensor, the second sensor, and the insulating material, wherein the first material layer is characterized by a first surface energy; a second material layer situated over a portion of the first material layer, wherein the portion of the first material layer is situated over the insulating material and not over the first sensor or the second sensor, wherein the second material layer is characterized by a second surface energy, the second surface energy being different from the first surface energy; a first lower well situated over the first sensor, the first lower well being a cavity in the insulating material, the cavity being lined by the first material layer; and a first upper well situated over the first lower well, the first upper well being a cavity in the second material layer.

[0014] In some aspects, the second surface energy is lower than the first surface energy.

[0015] In some aspects, an extent of the first upper well in a transverse direction is greater than an extent of the first lower well in the transverse direction.

[0016] In some aspects, the device further includes: a second lower well situated over the second sensor; and a second upper well situated over the second lower well, wherein an extent of the second upper well in the transverse direction is greater than an extent of the second lower well in the transverse direction. In some aspects, a volume of the second lower well differs from a volume of the first lower well. In some aspects, a volume of the second upper well and a volume of the first upper well are approximately equal.

[0017] In some aspects, the first sensor and the second sensor are magnetic sensors. In some aspects, the first sensor and the second sensor include magnetic tunnel junctions. Attorney Docket No. ROA-1004-WO / P39519-WO

[0018] In some aspects, the second material layer includes diamond-like carbon.

[0019] In some aspects, the first material layer includes a metal. In some aspects, the first material layer further includes an insulator over the metal. In some aspects, the metal includes gold.

[0020] In some aspects, the first material layer includes an oxide and the second material layer includes diamond-like carbon, or the first material layer includes a metal and the second material layer includes an oxide.

[0021] In some aspects, a thickness of the first material layer over the first sensor is less than or equal to about 30 nanometers (nm).

[0022] In some aspects, the insulating material includes an oxide.

[0023] In some aspects, the techniques described herein relate to a method of fabricating a device for sensing biomolecules, the method including: creating a plurality of capped sensors, the plurality of capped sensors including a plurality of sensors covered by respective caps of sacrificial material; encapsulating the plurality of capped sensors in an insulating material; performing a planarizing procedure on a surface of the insulating material to expose the sacrificial material over each capped sensor of the plurality of capped sensors; removing the sacrificial material from each capped sensor of the plurality of capped sensors, thereby exposing top surfaces of the plurality of sensors; and applying a layer of a first material over the exposed top surfaces of the plurality of sensors.

[0024] In some aspects, the method further includes: after applying the layer of the first material over the exposed top surfaces of the plurality of sensors, depositing a second material over a portion of the layer of the first material, wherein the portion of the layer of the first material is not situated over the plurality of sensors, and wherein a surface energy of the second material is lower than a surface energy of the first material.

[0025] In some aspects, the first material is hydrophilic; the second material is hydrophobic; or the first material is hydrophilic and the second material is hydrophobic.

[0026] In some aspects, depositing the second material over the portion of the layer of the first material includes at least one of chemical vapor deposition, physical vapor deposition (PVD), evaporation, sputtering, ion-beam deposition, pulsed laser deposition (PLD), atomic layer deposition (ALD), molecular beam epitaxy (MBE), electrodeposition, a sol-gel process, plasma- enhanced deposition (PECVD / PVD), spin coating, spray pyrolysis, electrophoretic deposition (EPD), or laser-assisted deposition.

[0027] In some aspects, creating the plurality of capped sensors includes performing photolithography or electron-beam lithography (EBL). Attorney Docket No. ROA-1004-WO / P39519-WO

[0028] In some aspects, creating the plurality of capped sensors includes depositing a sacrificial layer over the plurality of sensors. In some aspects, the sacrificial material includes diamond-like carbon (DLC) or parylene. In some aspects, depositing the sacrificial layer over the plurality of sensors includes using at least one of chemical vapor deposition, physical vapor deposition (PVD), evaporation, sputtering, ion-beam deposition, pulsed laser deposition (PLD), atomic layer deposition (ALD), molecular beam epitaxy (MBE), electrodeposition, a sol-gel process, plasma-enhanced deposition (PECVD / PVD), spin coating, spray pyrolysis, electrophoretic deposition (EPD), or laser-assisted deposition.

[0029] In some aspects, creating the plurality of capped sensors includes patterning the plurality of capped sensors. In some aspects, patterning the plurality of capped sensors includes performing etching.

[0030] In some aspects, encapsulating the plurality of capped sensors in the insulating material includes depositing the insulating material around each sensor of the plurality of capped sensors. In some aspects, encapsulating the plurality of capped sensors in the insulating material is performed using at least one of: chemical vapor deposition, physical vapor deposition (PVD), evaporation, sputtering, ion-beam deposition, pulsed laser deposition (PLD), atomic layer deposition (ALD), molecular beam epitaxy (MBE), electrodeposition, a sol-gel process, plasma- enhanced deposition (PECVD / PVD), spin coating, spray pyrolysis, electrophoretic deposition (EPD), or laser-assisted deposition.

[0031] In some aspects, performing the planarizing procedure on the surface of the insulating material to expose the sacrificial material over each sensor of the plurality of sensors includes performing chemical mechanical polishing.

[0032] In some aspects, removing the sacrificial material includes performing at least one of: selective wet chemistry, plasma etching, reactive ion etching (RIE), inductively coupled plasma etching, laser ablation, focused ion beam (FIB) etching, atomic layer etching (ALE), electrochemical etching, thermal etching, vapor phase etching, or ion implantation followed by selective etching.

[0033] In some aspects, applying the layer of the first material over the exposed top surfaces of the plurality of sensors includes performing at least one of: chemical vapor deposition, physical vapor deposition (PVD), evaporation, sputtering, ion-beam deposition, pulsed laser deposition (PLD), atomic layer deposition (ALD), molecular beam epitaxy (MBE), electrodeposition, a solgel process, plasma-enhanced deposition (PECVD / PVD), spin coating, spray pyrolysis, electrophoretic deposition (EPD), or laser-assisted deposition. Attorney Docket No. ROA-1004-WO / P39519-WO

[0034] BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Objects, features, and advantages of the disclosure will be readily apparent from the following description of certain embodiments taken in conjunction with the accompanying drawings in which:

[0036] FIGS. 1 A, IB, and 1C illustrate how certain manufacturing steps can result in variable sensitivities across sensors.

[0037] FIGS. 2A and 2B illustrate an example of a device for detecting molecules in accordance with some embodiments.

[0038] FIG. 2C is a closer view of a lower well and an upper well of a device for detecting molecules in accordance with some embodiments.

[0039] FIG. 3 is a flow diagram illustrating an example of a method that can be used to fabricate a device for sensing biomolecules in accordance with some embodiments.

[0040] FIGS. 4A, 4B, 4C, 4D, 4E, and 4F are representations of a device being fabricated at various points during a fabrication process in accordance with some embodiments.

[0041] To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the figures. Different instances of an element are labeled using a numeral followed by a letter. The specification sometimes refers to these elements collectively using only the number (e.g., sensors 105, caps 115, plurality of capped sensors 125).

[0042] It is contemplated that elements disclosed in one embodiment may be beneficially utilized in other embodiments without specific recitation. Moreover, the description of an element in the context of one drawing is applicable to other drawings illustrating that element.

[0043] DETAILED DESCRIPTION

[0044] One way to detect MNPs is by using magnetic sensors, which detect changes in the magnetic field caused by the presence of MNPs. When target molecules bound to MNPs are brought close to a magnetic sensor, the magnetic field changes, which can be measured as a shift in a property or characteristic of the sensor (e.g., electrical resistance, oscillation frequency, magnetic noise (mag-noise)).

[0045] To provide good detection sensitivity, it is desirable for MNPs to be as close as possible to the magnetic sensors that detect them. Generally speaking, the further the MNPs are from the sensors, the harder it is to detect them. Attorney Docket No. ROA-1004-WO / P39519-WO

[0046] Using current manufacturing technologies in conventional ways, it can be difficult to fabricate a detection device that allows the MNPs to be as close as desirable to the magnetic sensors. For example, the fabrication process may include a chemical-mechanical polishing (CMP) step. CMP combines both chemical and mechanical forces to remove excess material to smooth and flatten the surface of a silicon wafer during production. Typically, CMP involves using a rotating polishing pad that physically grinds or polishes the surface of the wafer. The wafer is pressed face-down against the pad while both rotate. The mechanical action is typically provided by applying a slurry. The slurry is generally a mixture of chemicals and particles. The chemicals react with the surface layer to weaken or dissolve it, and the particles (e.g., silica or alumina) provide abrasion and mechanically grind away material.

[0047] The goal of CMP is to make each layer of a chip perfectly flat before additional layers are added. In practice, however, at the scales of sensors for biomolecule detection, it is difficult to create perfectly flat surfaces using CMP. Although the combination of mechanical polishing and chemical etching can achieve both sufficient removal of excess material and adequate leveling of surfaces for some applications, at the small scale of biomolecules, the surface following a CMP step tends to be rough and uneven. The unevenness causes sensitivity problems, because some sensors are closer to biomolecules and others are further away.

[0048] FIGS. 1 A, IB, and 1C illustrate how the use of CMP can result in variable sensitivities across sensors. FIGS. 1 A, IB, and 1C show a device 10 at various points during the manufacturing process. At the point illustrated in FIG. 1 A, three sensors, namely a sensor 105 A, a sensor 105B, and a sensor 105C, have been patterned in the device 10. FIG. IB shows the device 10 after a layer of insulating material 110 has been deposited around the sensor 105 A, sensor 105B, and sensor 105C. FIG. 1C shows the device 10 after a CMP step. Because, at the scales of biomolecule detection, the surface of the device 10 is not perfectly flat, the distances between the sensors 105 and the MNPs to be detected vary from sensor to sensor. For example, as illustrated in FIG. 1C, the distance between the sensor 105A and the MNP 12A is greater than the distance between the sensor 105B and the MNP 12B, which is greater than the distance between the sensor 105C and the MNP 12C. If the device 10 were used to detect biomolecules, the sensor 105C would be more sensitive than both the sensor 105 A and the sensor 105B, and the sensor 105B would be more sensitive than the sensor 105 A. The different sensitivities result in less reliable / consistent detection than if the sensitivities of the sensors 105 were the same.

[0049] It is preferable for all sensors 105 to have substantially similar sensitivity so that it can be reliably determined whether individual sensors 105 are or are not detecting MNPs. Accordingly, Attorney Docket No. ROA-1004-WO / P39519-WO disclosed herein are methods of fabricating devices for sensing biomolecules (e.g., by sensing MNPs), and devices produced according to the disclosed methods. The disclosed techniques address various problems presented by current fabrication technology, including the limitations of CMP. The disclosed devices allow for more uniform distances between the sensors 105 and the biomolecules (and attached MNPs) to be sensed by those sensors 105, thereby improving the sensitivity consistency and overall performance of the device.

[0050] FIGS. 2A and 2B illustrate an example of a device 100 for detecting molecules in accordance with some embodiments. To assist in the explanation, rectangular-coordinate axes are shown in FIGS. 2A and 2B. FIG. 2A is a top view of the device 100 (in an x-y plane), and FIG. 2B is a cross-section view (in an x-z plane) of the device 100 at the position indicated in FIG. 2A. With reference to FIGS. 2A and 2B, the device 100 includes a substrate 101, a plurality of sensors 105, insulating material 110, a first material layer 120, a second material layer 130, a plurality of lower wells 140, and a plurality of plurality of upper wells 150. The device 100 can include other elements that are not specifically illustrated or discussed (e.g., electrodes, additional layers, vias, traces, etc.).

[0051] In the example shown, the plurality of sensors 105 includes a sensor 105 A, a sensor 105B, and a sensor 105C. In general, the sensors 105 can be any type of magnetic sensor that is capable of detecting magnetic particles (e.g., MNPs). For example, the sensors 105 can be anisotropic magnetoresistance (AMR) sensors. AMR sensors work based on the anisotropic magnetoresistance effect, which describes how the electrical resistance of a ferromagnetic material changes depending on the angle between the direction of current flow and the orientation of the magnetic field. When the magnetization of the ferromagnetic material is parallel to the direction of the current, the resistance is lower. When the magnetization is perpendicular to the current, the resistance increases. Changes in resistance as the magnetic field alters the magnetization direction can be detected and used to measure the magnetic field strength or direction. AMR sensors include linear AMR sensors designed to detect magnetic fields that vary linearly over a range, differential AMR sensors (e.g., having two sensor elements in a bridge configuration to measure the difference in the magnetic field between the two sensor elements, which enhances sensitivity and cancels out common-mode noise or interference), rotational (or angle) AMR sensors that measure the angle of rotation of a magnetic field by detecting the angular position of the magnetic field relative to the sensor, Wheatstone bridge AMR sensors (having four resistive elements connected in a Wheatstone bridge), AMR current sensors that measure the magnetic field generated by a current flowing through a conductor, Attorney Docket No. ROA-1004-WO / P39519-WO

[0052] AMR proximity sensors that detect the presence or absence of a MNP by sensing changes in the magnetic field.

[0053] As another example, the sensors 105 can be giant magnetoresistance (GMR) sensors. GMR sensors use the giant magnetoresistance effect to detect changes in magnetic fields. The GMR effect occurs when the electrical resistance of a multilayer structure (typically alternating layers of electrically-conducting ferromagnetic and non-magnetic materials) changes in response to the relative alignment of magnetizations in the ferromagnetic layers. The ferromagnetic layers are typically made of materials like cobalt (Co), nickel (Ni), or iron (Fe). One layer is “pinned” (its magnetization is fixed in a certain direction), while the other layer is “free” to align with the external magnetic field. The non-magnetic spacer layer is typically a thin layer of a material (e.g., copper (Cu)). The GMR effect is particularly strong when the electrically-conducting layers are very thin, on the order of a few nanometers. When the magnetization of the two ferromagnetic layers is aligned (parallel), the resistance of the sensor is low. When the magnetization of the two layers is anti-aligned (antiparallel), the resistance is high. By measuring the change in resistance, GMR sensors can detect the magnitude and direction of an external magnetic field. GMR sensors include multilayer GMR sensors having multiple layers of alternating electrically-conducting ferromagnetic and non-magnetic materials. The GMR effect arises from the interactions between the layers, and the magnitude of the resistance change is proportional to the number of layers. Spin-valve GMR sensors, which have two ferromagnetic layers separated by a non-magnetic spacer. One layer is pinned, and the other is free to respond to the external magnetic field.

[0054] As another example, the sensors 105 can be tunnel magnetoresistance (TMR) sensors. TMR sensors a type of magnetoresistive sensor that uses the tunnel magnetoresistance effect to detect magnetic fields. The TMR effect is based on quantum mechanical tunneling, whereby electrons can tunnel through a thin insulating barrier between two ferromagnetic layers. The electrical resistance of the structure changes depending on the relative alignment of the magnetizations in the two ferromagnetic layers. When the magnetizations of the two ferromagnetic layers are aligned (parallel), the tunneling resistance is low, allowing more electrons to pass through. When the magnetizations are misaligned (antiparallel), the resistance increases, reducing the electron tunneling. By detecting changes in resistance as a function of the external magnetic field, TMR sensors can measure the field's strength and direction. A TMR sensor typically includes a pinned ferromagnetic layer that has a fixed magnetization direction (usually pinned by an antiferromagnetic layer), a free ferromagnetic layer that has a magnetization that is free to rotate Attorney Docket No. ROA-1004-WO / P39519-WO in response to external magnetic field, and a thin (nanometer-scale) insulating layer (e.g., magnesium oxide (MgO)) between the two ferromagnetic layers. Electrons can tunnel through the insulating layer depending on the relative orientation of the ferromagnetic layers. TMR sensors have a high magnetoresistance ratio, which makes them more sensitive to changes in magnetic fields than AMR and GMR sensors. In addition, TMR sensors typically consume less power than alternative magnetic sensors, exhibit excellent signal-to-noise ratios, and offer stable performance across a wide range of temperatures. TMR sensors can also be scaled down to very small sizes.

[0055] As another example, the sensors 105 can be spin-valve sensors. Spin-valve sensors are a type of MR sensor that operates based on the GMR effect. Spin valves typically consist of two ferromagnetic layers separated by a non-magnetic spacer layer, where one ferromagnetic layer is “pinned” or fixed, and the other layer is “free” to align with an external magnetic field. The relative orientation of these layers influences the resistance of the sensor, enabling magnetic field detection. A spin-valve sensor can be a current-in-plane (CIP) spin-valve sensor in which the electrical current flows in-plane, parallel to the magnetic layers, or a current-perpendicular-to- plane (CPP) spin-valve sensor, in which the current flows perpendicularly to the plane of the layers rather than parallel (as in the standard configuration). The CPP approach allows for improved scalability and higher sensitivity as the sensor size decreases.

[0056] Spin-valve sensors include standard GMR spin-valve sensors, which include electrically- conducting layers, typically a pinned magnetic layer, a free magnetic layer, and a non-magnetic spacer (e.g., copper). The resistance of a standard GMR spin-valve senor changes based on whether the magnetic moments of the two layers are aligned (low resistance) or anti-aligned (high resistance). Another example of a spin-valve sensors is the synthetic antiferromagnet spinvalve sensor, in which the pinned layer is replaced by a synthetic antiferromagnet (SAF), which includes two ferromagnetic layers separated by a non-magnetic spacer. The layers are coupled antiferromagnetically, increasing the stability of the pinned layer and reducing noise. Another example of a spin-valve sensor is the top-spin-valve sensor, in which the free magnetic layer is placed above the non-magnetic spacer layer, whereas the pinned layer is located below it. The configuration can be optimized for certain applications where the magnetic field is applied in a specific direction. Similarly, bottom-spin-valve sensors have a configuration that is similar to the top-spin-valve, except that the pinned layer is on the top and the free layer is below the nonmagnetic spacer. This arrangement also alters the magnetic response based on the field orientation. Another example of a spin-valve sensor is an exchange-biased spin-valve sensor, in Attorney Docket No. ROA-1004-WO / P39519-WO which the pinned magnetic layer is stabilized by an adjacent antiferromagnetic layer. The interaction between the ferromagnetic and antiferromagnetic layers creates a unidirectional anisotropy, thereby “pinning” the magnetization in one direction. Another example of a spinvalve sensor is a tunneling spin-valve sensor, which combines the principles of both spin-valve and TMR sensors. Instead of a metallic spacer, a thin insulating barrier is used, and electrons tunnel through the barrier depending on the relative alignment of the magnetic layers. Another example is dual spin-valve sensors, which use two spin-valve structures in tandem. This configuration increases the total resistance change and enhances the sensor’s sensitivity and performance in detecting small magnetic fields.

[0057] As another example, the sensors 105 can be extraordinary magnetoresistance (EMR) sensors. EMR sensors are specialized devices that detect changes in magnetic fields by using the extraordinary magnetoresistance effect, which is a phenomenon observed in certain semiconductor / metal hybrid structures, where the resistance of the device changes dramatically in the presence of an external magnetic field. When no magnetic field is present, current flows uniformly across the sensor. When an external magnetic field is applied, the path of the current is altered due to the Lorentz force, leading to a change in resistance. The change in resistance is directly proportional to the strength of the magnetic field, which can be measured and used to determine the field strength and direction.

[0058] As another example, the sensors 105 can be hybrid magnetoresistive sensors that combine two or more types of magnetoresistive effects, such as GMR and TMR, to achieve enhanced sensitivity and better performance across a wider range of magnetic fields.

[0059] In some embodiments, the sensors 105 are TMR sensors, such as magnetic tunnel junction (MTJ) sensors, which, as explained above, offer high sensitivity and can be miniaturized.

[0060] With continuing reference to FIGS. 2A and 2B, the sensors 105 are encapsulated in insulating material 110. As a result, insulating material 110 is situated between the sensor 105 A and the sensor 105B, and between the sensor 105B and the sensor 105C. The insulating material 110 prevents electrical short circuits, isolates the sensors 105 from each other, and protects the device 100 from environmental factors. The insulating material 110 can be any material that has suitable electrical insulation properties, thermal stability, and mechanical strength. For example, the insulating material 110 can comprise one or more of silicon dioxide (SiCE) (also referred to as silica), silicon nitride (SisN^, one or more low-k dielectric materials (e.g., organosilicate glass (OSG), polyimide-based dielectrics, fluorinated silica (FSG)), a polyimide, hafnium oxide Attorney Docket No. ROA-1004-WO / P39519-WO

[0061] (HfCE), aluminum oxide (AI2O3) (also referred to as alumina), boron nitride (BN), an epoxy resin, or tetraethyl orthosilicate (TEOS).

[0062] With continuing reference to FIGS. 2A and 2B, the device 100 example includes a first material layer 120 situated over the sensors 105 and the insulating material 110. In some embodiments, the first material layer 120 is a contiguous layer (i.e., when viewed from above (e.g., as shown in FIG. 2A), there are no breaks in the first material layer 120). The first material layer 120 is characterized by a first surface energy, which can be expressed in units of energy per unit area. As will be appreciated by those having ordinary skill in the art, surface energy represents the excess energy at the surface of a material compared to its bulk, which arises because surface atoms or molecules are not surrounded by other atoms or molecules in all directions, which leads to unsatisfied bonds. This imbalance creates a higher energy state at the surface. As will be appreciated, surface energy can change with temperature, humidity, and surrounding chemical environment.

[0063] Surface energy determines how well a liquid spreads on a solid. Materials with low surface energy tend to repel water and particles. Metals typically have high surface energies due to strong metallic bonds. Ceramics also have high surface energies influenced by ionic or covalent bonding. In contrast, polymers typically have lower surface energies because of weaker intermolecular forces. Chemical composition, oxidation, and surface treatments (e.g., coatings) can alter surface energy. Materials with high surface energy are generally hydrophilic. Hydrophilic materials have an affinity for water and can absorb or attract water molecules. Materials with low surface energy can be, but are not required to be, hydrophobic.

[0064] The first material layer 120 can comprise any suitable native or treated material, such as one or more of silicon dioxide (SiCE) (also referred to as silica), silicon nitride (SisN^, polyvinyl alcohol (PVA), titanium dioxide (TiCE), aluminum oxide (AECE) (also referred to as alumina), polydimethylsiloxane (PDMS), a water-soluble photoresist, or a polyimide.

[0065] In some embodiments, the first material layer 120 comprises a metal overlaid by another material. For example, the first material layer 120 can comprise gold overlaid by an oxide (e.g., silicon dioxide (SiCE), titanium dioxide (TiCE), aluminum oxide (AI2CE)).

[0066] In some embodiments, the first material layer 120 is thin. For example, the thickness of the first material layer 120 can be less than about 30 nanometers (nm). Because the thickness of the first material layer 120 essentially determines the distance between settled MNPs and respective sensors 105, providing a first material layer 120 that is thin (and substantially uniform in Attorney Docket No. ROA-1004-WO / P39519-WO thickness) allows the sensitivities of the sensors 105 to be substantially uniform, which helps to improve the reliability and uniformity of readings.

[0067] In some embodiments, the thickness of the first material layer 120 can be adjusted (e.g., tuned) to control for sensitivity, which may be dependent on the use or purpose of the device 100. For example, the thickness of the first material layer 120 can differ for different applications (e.g., a type of targeted MNP) used with the device 100. In some embodiments, a first instance of the device 100 can be interchangeable (e.g., as a replacement cartridge) with a second instance of the device 100, where the first and second instances differ in some way (e.g., configuration, material(s)), and both the first and second instances of the device 100 are compatible with a sensing system (e.g., a sequencer, a diagnostic system) that uses the device 100.

[0068] With continued reference to FIGS. 2A and 2B, the device 100 example also includes a second material layer 130. The second material layer 130 has a second surface energy that is lower than the first surface energy of the first material layer 120. As explained above, materials with lower surface energies tend to repel water. The second material layer 130 can comprise any suitable native or treated material, such as one or more of polytetrafluoroethylene (PTFE), octadecyltrichlorosilane (OTS), a fluorinated polymer (e.g., a perfluoropolyether (PFPE), fluorosilicone), hexamethyldisilazane (HMDS), hydrophobic silicon dioxide (SiCE) (i.e., silicon dioxide with an applied hydrophobic coating or surface treatment, such as silane coupling agents (e.g., OTS or HMDS)), a self-assembled monolayer (SAM) (a molecular layer that spontaneously forms on surfaces, e.g., comprising OTS or other alkylsilane molecules to create monolayers on silicon or metal surfaces), diamond-like carbon (DLC), fluorinated DLC, silicon nitride (SisN^ with hydrophobic treatment (e.g., to make its surface non-wetting), a fluorosilane coating, or parylene.

[0069] In some embodiments, the second material layer 130 comprises a DLC film. A DLC film is an amorphous carbon film with a structure similar to diamond. The surface of a DLC film has low surface energy, which reduces the ability of water to spread out on the material, leading to the formation of water droplets rather than allowing the water to adhere or wet the surface. If desired, in embodiments in which the second material layer 130 comprises a DLC film, the degree of hydrophobicity can be enhanced through specific surface treatments or modifications to the DLC composition. For example, in some embodiments, the second material layer 130 comprises a fluorinated DLC film.

[0070] As shown in the example of FIGS. 2A and 2B, the second material layer 130 is situated over a portion of the first material layer 120. Specifically, the second material layer 130 is situated Attorney Docket No. ROA-1004-WO / P39519-WO over the part(s) of the first material layer 120 that are primarily over the insulating material 110. Unlike the first material layer 120, which is a contiguous layer, the second material layer 130 is non-contiguous (i.e., when viewed from above (e.g., as shown in FIG. 2A), there are breaks / discontinuities in the second material layer 130, which is not situated over the sensors 105). As a result of the positions of the first material layer 120 and the second material layer 130, the device 100 example shown in FIGS. 2A and 2B includes a plurality of lower wells 140 and a plurality of upper wells 150. The lower wells 140 and the upper wells 150 are non-overlapping. In this context, non-overlapping means that the volumes of the lower wells 140 and the volumes of the upper wells 150 can touch (e.g., share a boundary), but they do not share any common volume. It will be appreciated that in the examples illustrated by the figures herein, the empty space that includes the lower wells 140 and the upper wells 150 is at least partially contiguous, and therefore the identification of separate lower wells 140 and upper wells 150 is largely for convenience of description. As shown and described, in some embodiments, the lower wells 140 are cavities in the insulating material 110, where the cavities are lined by the first material layer 120, and the upper wells 150 are cavities in the second material layer 130.

[0071] In the example illustrated in FIGS. 2A and 2B, the device 100 includes a lower well 140A, a lower well 140B, and a lower well 140C. The lower wells 140 are situated over respective ones of the sensors 105. The lower wells 140 are cavities in the insulating material 110, which are covered (or lined) by the first material layer 120. In the view of FIG. 2A, the lower wells 140 appear as indentations in the first material layer 120, and in the view of FIG. 2B, they appear as trenches in the first material layer 120.

[0072] The device 100 also includes an upper well 150A situated over the lower well 140A, an upper well 150B situated over the lower well 140B, and an upper well 150C situated over the lower well 140C. The upper wells 150 are cavities (or gaps) in the second material layer 130. In the view of FIG. 2 A, they appear as missing portions of the second material layer 130, and in the view of FIG. 2B, they appear as trenches in the second material layer 130.

[0073] An objective of the first material layer 120, the second material layer 130, the lower wells 140, and the upper wells 150 of the device 100 example is to encourage the molecules for detection to settle in the regions in which the sensors 105 are most likely to be able to sense them. In the illustrated example, those regions are directly above the sensors 105. The second material layer 130 discourages molecules from settling in regions that are too far from the sensors 105 for detection to be reliable. The first material layer 120 encourages molecules to Attorney Docket No. ROA-1004-WO / P39519-WO settle in at least the upper wells 150, and ideally in the lower wells 140 where they will be closest to the sensors 105.

[0074] In some embodiments, the first material layer 120 comprises an oxide, and the second material layer 130 comprises DLC. In some such embodiments, silanes can be used to bind molecules for detection to the first material layer 120 and not to the second material layer 130.

[0075] In some embodiments, the first material layer 120 comprises a metal (e.g., gold), and the second material layer 130 comprises an oxide. In some such embodiments, a thiol can be used to bind molecules for detection to the first material layer 120 and not to the second material layer 130.

[0076] In some embodiments, all of the upper wells 150 of the device 100 have substantially the same volume. In other words, in some embodiments, the volumes of all of the upper wells 150 are approximately equal.

[0077] In some embodiments, two or more of the lower wells 140 have different volumes. For example, in the device 100 example shown in FIG. 2B, the lower well 140 A, the lower well MOB, and the lower well 140C have different depths relative to the local portion of the second material layer 130 (and relative to the local upper surface of the first material layer 120). This difference in the volumes of the lower wells 140 can be due, for example, to non-uniformities caused by manufacturing processes such as CMP. In some embodiments, the shapes of the lower wells 140 are substantially the same in the x-y plane, and, as a result, the volumes of two or more of the lower wells 140 are different. For example, in the example of FIG. 2A, the shapes and sizes of the lower well 140A, the lower well 140B, and the lower well 140C are substantially the same in the x-y plane (substantially circular with a consistent radius), and the volumes of the lower well 140 A, the lower well MOB, and the lower well 140C shown in FIG. 2B are different because the depths of the lower well 140 A, lower well MOB, and lower well 140C relative to the second material layer 130 are different. Specifically, in the illustrated example, the volume of the lower well 140C is less than the volume of the lower well MOB, which is less than the volume of the lower well 140A.

[0078] An important feature of the device 100 is that even though the volumes of the lower wells 140 are different, the distance between the bottom surface of the lower wells 140, where MNPs should settle, and the tops of the sensors 105 underneath the lower wells 140 (in the z-direction) is approximately the same. This aspect of the device 100 represents a significant improvement over the configuration shown and discussed in the context of FIGS. 1 A, IB, and 1C. Whereas the sensors 105 of the device 10 shown in FIGS. 1A, IB, and 1C have different sensitivities because Attorney Docket No. ROA-1004-WO / P39519-WO of their different distances (in the z-direction) from where MNPs could be, the sensors 105 of the device 100 shown and described in FIGS. 2A and 2B all have substantially the same sensitivity because all of the sensors 105 are approximately the same distance from where MNPs should settle.

[0079] The device 100 illustrated in FIGS. 2A and 2B is merely an example. An implementation can differ from the example. For example, although the device 100 example shown in FIGS. 2 A and 2B includes three sensors 105, the device 100 can include more or fewer than three sensors 105. In general, the device 100 can include any number of sensors 105. Furthermore, although FIGS. 2A and 2B illustrate the sensors 105 in a linear arrangement, the sensors 105 can be arranged in any suitable manner (e.g., in a rectangular grid pattern, in a hexagonal pattern, in no particular pattern). In addition, although FIGS. 2A and 2B suggest the sensors 105 are cylindrical, the sensors 105 can have any suitable shape or configuration.

[0080] FIG. 2C is a closer view of a lower well 140 and an upper well 150 in accordance with some embodiments. The axes in FIG. 2C are in a d-z plane, where d is a transverse direction, that is, a selected direction in an x-y plane, assuming use of the rectangular coordinate system shown in FIGS. 2A and 2B. The lower well 140 has a transverse extent 141 in the transverse direction, and the upper well 150 has a transverse extent 151 in the transverse direction. The transverse extent 141 of a lower well 140 is its maximum or average width in some transverse direction of an x-y plane, and the transverse extent 151 of the upper well 150 is its maximum or average width in some transverse direction of an x-y plane. In some embodiments, the transverse extent 141 of each of the lower wells 140 in one or more selected directions d is approximately the same. In some embodiments, the transverse extent 151 of each of the upper wells 150 in one or more selected directions d is approximately the same.

[0081] In some embodiments, the transverse extent 151 of the upper wells 150 is larger than the transverse extent 141 of the lower wells 140 for all possible directions d. For example, in the example of the device 100 shown in FIG. 2A, the transverse extent 151 is larger than the transverse extent 141 for all possible directions d in the x-y plane. In some embodiments, the transverse extent 151 is larger than the transverse extent 141 for at least one direction d. In some embodiments, the transverse extent 151 of the upper wells 150 is smaller than the transverse extent 141 of the lower wells 140 for all possible directions d. In some embodiments, the transverse extent 151 is smaller than the transverse extent 141 for at least one direction d.

[0082] It is to be appreciated that the slopes of the first material layer 120 and second material layer 130 shown in FIGS. 2B and 2C are merely illustrative. In an implementation, the surfaces of the Attorney Docket No. ROA-1004-WO / P39519-WO first material layer 120 and the second material layer 130 may be irregular and / or non-monotonic due to variability and / or imperfections introduced in fabrication processes (e.g., in a CMP step). FIGS. 2A, 2B, and 2C are not intended to be limiting.

[0083] FIG. 3 is a flow diagram illustrating an example of a method 300 that can be used to fabricate a device for sensing biomolecules (e.g., a device 100) in accordance with some embodiments. FIGS. 4 A, 4B, 4C, 4D, 4E, and 4F are representations of a device 100 being fabricated at various points during the manufacturing process using the method 300.

[0084] At block 302, the method 300 begins. At block 304, a plurality of capped sensors 125 is created. The plurality of capped sensors 125 comprises a plurality of sensors 105 covered by respective caps 115 of sacrificial material. FIG. 4A is a representation of the device 100 after formation of a plurality of capped sensors 125, including a capped sensor 125A, a capped sensor 125B, and a capped sensor 125C in accordance with some embodiments. The capped sensor 125A comprises a cap 115A situated over the sensor 105A, the capped sensor 125B comprises a cap 115B is situated over a sensor 105B, and the capped sensor 125C comprises a cap 115C situated over a sensor 105C. FIG. 4A thus illustrates features of the device 100 during the fabrication process after completion of block 304 of the method 300.

[0085] Block 304 can be accomplished, for example, by patterning the plurality of capped sensors 125 to define the geometry and dimensions of the plurality of capped sensors 125. As a specific example, in some embodiments, the plurality of capped sensors 125 comprises MTJs as the sensors 105, and block 304 can be accomplished by patterning the MTJs. In some embodiments, block 304 comprises a photolithography process in which a photosensitive resist layer is applied, the photosensitive resist layer is exposed to light through a mask, and the exposed (or unexposed, depending on the resist type) areas are developed to form a pattern. Alternatively, block 304 can comprise an electron-beam lithography (EBL) process (e.g., for precise, small- scale patterning). In some embodiments, block 304 comprises performing etching (e.g., to transfer the pattern defined by lithography onto the layers of materials). Etching techniques include ion beam etching (IBE) and reactive ion etching (RIE), for example. In some embodiments, block 304 includes depositing layers for the sensors 105 (e.g., ferromagnetic layers and a tunnel barrier), which can be accomplished using methods such as sputtering, ionbeam deposition, or molecular beam epitaxy (MBE). In some embodiments, after patterning the resist layer, material is deposited, and then the resist is dissolved, which “lifts off’ the unwanted material and leaves the sensor pattern behind. In some embodiments, after patterning, the sensors 105 are annealed to improve crystallinity and enhance the TMR effect. Attorney Docket No. ROA-1004-WO / P39519-WO

[0086] The cap 115A, cap 115B, and cap 115C can comprise any suitable sacrificial material. In some embodiments, the sacrificial material comprises DLC. In some embodiments, the sacrificial material comprises parylene. In some embodiments, creating the caps 115 comprises depositing the sacrificial material over each of the sensors 105 (e.g., as part of the patterning process).

[0087] At block 306, the plurality of capped sensors 125 is encapsulated in an insulating material (e.g., insulating material 110). In some embodiments, block 306 comprises depositing the insulating material 110 around and over each of the plurality of capped sensors 125. FIG. 4B is a representation of the device 100 during the manufacturing process with a plurality of capped sensors 125 following the encapsulation in insulating material 110 at block 306 of the method 300 in accordance with some embodiments.

[0088] Any suitable process can be used to perform block 306. For example, encapsulating the plurality of capped sensors 125 in the insulating material 110 can be performed using at least one of chemical vapor deposition, physical vapor deposition (PVD), evaporation, sputtering, ionbeam deposition, pulsed laser deposition (PLD), atomic layer deposition (ALD), molecular beam epitaxy (MBE), electrodeposition, a sol-gel process, plasma-enhanced deposition (PECVD / PVD), spin coating, spray pyrolysis, electrophoretic deposition (EPD), or laser-assisted deposition.

[0089] Referring again to FIG. 3, at block 308, a planarizing procedure is performed on a surface of the insulating material 110 to expose the sacrificial material over each capped sensor of the plurality of capped sensors 125 (to expose the caps 115). In some embodiments, the planarizing procedure comprises CMP, described above. FIG. 4C is a representation of the device 100 during the manufacturing process following the planarizing procedure performed at block 308 of the method 300 in accordance with some embodiments. Note that in the illustration of FIG. 4C, the result of block 308 is that, in the example, the top surface of the device 100 is uneven. Although FIG. 4C shows a consistent downward slope from left to right, it is to be appreciated that the surface could be different from that shown (e.g., the surface could be irregular and / or nonmonotonic).

[0090] Referring again to FIG. 3, at block 310, the caps 115 are removed by removing the sacrificial material from each capped sensor of the plurality of capped sensors 125, thereby exposing top surfaces of the plurality of sensors 105. FIG. 4D is a representation of the device 100 during the manufacturing process following the removal of the caps 115 at block 310 of the method 300 in accordance with some embodiments. Attorney Docket No. ROA-1004-WO / P39519-WO

[0091] The sacrificial material (the caps 115) can be removed using any suitable technique. For example, the sacrificial material (the caps 115) can be removed by performing selective wet chemistry (e.g., chemical processes in which certain materials or components are selectively etched, deposited, or processed using liquid-phase chemical reactions). As another example, block 310 can be performed using dry etching (e.g., plasma etching, reactive ion etching (RIE), inductively coupled plasma etching). As another example, block 310 can be performed using laser ablation (e.g., using high-energy laser pulses to remove material from a surface by vaporizing it). As yet another example, block 310 can be performed using a focused ion beam (FIB) (e.g., using a focused beam of ions (often gallium) to sputter or mill away material from a surface). As another example, block 310 can be performed using atomic layer etching (ALE) (a highly controlled, layer-by-layer etching process similar to atomic layer deposition (ALD) that uses alternating chemical reactions to selectively etch materials with atomic-scale precision). As another example, block 310 can be performed using electrochemical etching (e.g., applying an electric current in a solution and controlling the electrochemical reaction between the substrate and the electrolyte). As another example, block 310 can be performed using thermal or vapor phase etching (e.g., selective etching that uses high-temperature gases that react with the material to be removed). As another example, block 310 can be performed using ion implantation to introduce defects in the sacrificial material followed by selective etching in which the damaged or modified areas are removed chemically or physically.

[0092] Referring again to FIG. 3, at block 312, a first material layer (e.g., the first material layer 120) is applied over the exposed top surfaces of the sensors 105. The first material layer 120 has a first surface energy, as explained above. FIG. 4E is a representation of the device 100 during the manufacturing process following the application of the first material layer 120 at block 312 of the method 300 in accordance with some embodiments.

[0093] As explained above, the first material layer 120 can comprise any suitable native or treated material (e.g., silicon dioxide (SiCE), silicon nitride (SisN^, polyvinyl alcohol (PVA), titanium dioxide (TiCE), aluminum oxide (AECE), poly dimethyl siloxane (PDMS), a water-soluble photoresist, a polyimide, a metal overlaid by a hydrophilic material (e.g., gold overlaid by an oxide)). The first material layer 120 can be applied in any suitable way, such as, for example, using at least one of chemical vapor deposition, physical vapor deposition (PVD), evaporation, sputtering, ion-beam deposition, pulsed laser deposition (PLD), atomic layer deposition (ALD), molecular beam epitaxy (MBE), electrodeposition, a sol-gel process, plasma-enhanced Attorney Docket No. ROA-1004-WO / P39519-WO deposition (PECVD / PVD), spin coating, spray pyrolysis, electrophoretic deposition (EPD), or laser-assisted deposition.

[0094] Referring again to FIG. 3, optionally, at block 314, after applying the first material layer 120 over the exposed top surfaces of the plurality of sensors 105, a second material (e.g., the second material layer 130) is deposited over a portion of the first material layer 120, wherein the portion of the first material layer 120 is not situated over the plurality of sensors 105. As explained above in the discussion of FIGS. 2A, 2B, and 2C, the material of the second material layer 130 has a lower surface energy than the material of the first material layer 120. The objective is for the second material layer 130 to encourage biomolecules to settle on top of the exposed portion of the first material layer 120.

[0095] If included, the second material layer 130 can comprise any suitable native or treated material with a sufficiently low surface energy (e.g., lower than the surface energy of the material of the first material layer 120), such that a tethering element is encouraged to bind to the first material layer 120 and not to the second material layer 130. Although it may be desirable for the second material layer 130 to be hydrophobic (e.g., for non-fouling), hydrophobicity is not a requirement. Examples of materials that can be used as or included in the second material layer 130 are DLC, fluorinated DLC, polytetrafluoroethylene (PTFE), octadecyltrichlorosilane (OTS), a fluorinated polymer (e.g., a perfluoropolyether (PFPE), fluorosilicone), hexamethyldisilazane (HMDS), hydrophobic silicon dioxide (SiCE) (i.e., silicon dioxide with an applied hydrophobic coating or surface treatment, such as silane coupling agents (e.g., OTS or HMDS)), a selfassembled monolayer (SAM) (a molecular layer that spontaneously forms on surfaces, e.g., comprising OTS or other alkylsilane molecules to create monolayers on silicon or metal surfaces), silicon nitride (SisN^ with hydrophobic treatment (e.g., to make its surface nonwetting), a fluorosilane coating, or parylene The second material layer 130 can be deposited using any suitable technique, such as, for example, at least one of chemical vapor deposition, physical vapor deposition (PVD), evaporation, sputtering, ion-beam deposition, pulsed laser deposition (PLD), atomic layer deposition (ALD), molecular beam epitaxy (MBE), electrodeposition, a sol-gel process, plasma-enhanced deposition (PECVD / PVD), spin coating, spray pyrolysis, electrophoretic deposition (EPD), or laser-assisted deposition.

[0096] FIG. 4F is a representation of the device 100 following the application of the second material layer 130 at optional block 314 of the method 300 in accordance with some embodiments. A key aspect shown in FIG. 4F and other drawings herein is that the regions directly above the sensors 105 are substantially uniform, even if one or more non-uniform Attorney Docket No. ROA-1004-WO / P39519-WO process steps such as CMP were used to perform block 308 of the method 300. For example, referring to both FIG. 4F and FIG. 2B, the distances from the tops of the sensors 105 to the bottoms of the lower wells 140 are the same for all of the sensors 105, even though the volumes of the lower wells 140 differ. Thus, a molecule that settles in the lower well 140A of the sensor 105 A should be detected as reliably as a molecule that settles in the lower well 140C of the sensor 105C.

[0097] Referring again to FIG. 3, at block 316, the method 300 ends.

[0098] Any suitable technology or technologies can be used to perform the method 300. In some embodiments, some or all of the method 300 is performed in CMOS.

[0099] In the foregoing description and in the accompanying drawings, specific terminology has been set forth to provide a thorough understanding of the disclosed embodiments. In some instances, the terminology or drawings may imply specific details that are not required to practice the invention.

[0100] Although some of the examples described herein include MTJ sensors, it is to be appreciated that the sensors 105 can be other types of sensors.

[0101] To avoid obscuring the present disclosure unnecessarily, well-known components are shown in block diagram form and / or are not discussed in detail or, in some cases, at all.

[0102] Unless otherwise specifically defined herein, all terms are to be given their broadest possible interpretation, including meanings implied from the specification and drawings and meanings understood by those skilled in the art and / or as defined in dictionaries, treatises, etc. As set forth explicitly herein, some terms may not comport with their ordinary or customary meanings.

[0103] As used in the specification and the appended claims, the singular forms “a,” “an” and “the” do not exclude plural referents unless otherwise specified. The word “or” is to be interpreted as inclusive unless otherwise specified. Thus, the phrase “A or B” is to be interpreted as meaning all of the following: “both A and B,” “A but not B,” and “B but not A.” Any use of “and / or” herein does not mean that the word “or” alone connotes exclusivity.

[0104] As used in the specification and the appended claims, phrases of the form “at least one of A, B, and C,” “at least one of A, B, or C,” “one or more of A, B, or C,” and “one or more of A, B, and C” are interchangeable, and each encompasses all of the following meanings: “A only,” “B only,” “C only,” “A and B but not C,” “A and C but not B,” “B and C but not A,” and “all of A, B, and C.” Attorney Docket No. ROA-1004-WO / P39519-WO

[0105] To the extent that the terms “include(s),” “having,” “has,” “with,” and variants thereof are used in the detailed description or the claims, such terms are intended to be inclusive in a manner similar to the term “comprising,” i.e., meaning “including but not limited to.”

[0106] The terms “exemplary” and “embodiment” are used to express examples, not preferences or requirements.

[0107] The term “coupled” is used herein to express a direct connection / attachment as well as a connect! on / attachm ent through one or more intervening elements or structures.

[0108] The terms “over,” “under,” “between,” and “on” are used herein refer to a relative position of one feature with respect to other features. For example, one feature disposed “over” or “under” another feature may be directly in contact with the other feature or may have intervening material. Moreover, one feature disposed “between” two features may be directly in contact with the two features or may have one or more intervening features or materials. In contrast, a first feature “on” a second feature is in contact with that second feature.

[0109] The term “substantially” is used to describe a structure, configuration, dimension, etc. that is largely or nearly as stated, but, due to manufacturing tolerances and the like, may in practice result in a situation in which the structure, configuration, dimension, etc. is not always or necessarily precisely as stated. For example, describing two lengths as “substantially equal” means that the two lengths are the same for all practical purposes, but they may not (and need not) be precisely equal at sufficiently small scales. As another example, a structure that is “substantially vertical” would be considered to be vertical for all practical purposes, even if it is not precisely at 90 degrees relative to horizontal.

[0110] The drawings are not necessarily to scale, and the dimensions, shapes, and sizes of the features may differ substantially from how they are depicted in the drawings.

[0111] Although specific embodiments have been disclosed, it will be evident that various modifications and changes may be made thereto without departing from the broader spirit and scope of the disclosure. For example, features or aspects of any of the embodiments may be applied, at least where practicable, in combination with any other of the embodiments or in place of counterpart features or aspects thereof. Accordingly, the specification and drawings are to be regarded in an illustrative rather than a restrictive sense.

Claims

Attorney Docket No. ROA-1004-WO / P39519-WOCLAIMS1. A device for sensing biomolecules, the device comprising: a plurality of sensors, including a first sensor and a second sensor; insulating material situated between the first sensor and the second sensor; a first material layer situated over the first sensor, the second sensor, and the insulating material, wherein the first material layer is characterized by a first surface energy; a second material layer situated over a portion of the first material layer, wherein the portion of the first material layer is situated over the insulating material and not over the first sensor or the second sensor, wherein the second material layer is characterized by a second surface energy, the second surface energy being different from the first surface energy; a first lower well situated over the first sensor, the first lower well being a cavity in the insulating material, the cavity being lined by the first material layer; and a first upper well situated over the first lower well, the first upper well being a cavity in the second material layer.

2. The device recited in claim 1, wherein the second surface energy is lower than the first surface energy.

3. The device recited in claim 1 or claim 2, wherein an extent of the first upper well in a transverse direction is greater than an extent of the first lower well in the transverse direction.

4. The device recited in claim 3, further comprising: a second lower well situated over the second sensor; and a second upper well situated over the second lower well, wherein an extent of the second upper well in the transverse direction is greater than an extent of the second lower well in the transverse direction.

5. The device recited in claim 4, wherein: a volume of the second lower well differs from a volume of the first lower well.

6. The device recited in claim 5, wherein a volume of the second upper well and a volume of the first upper well are approximately equal.Attorney Docket No. ROA-1004-WO / P39519-WO7. The device recited in any one of claims 1 to 6, wherein the first sensor and the second sensor are magnetic sensors.

8. The device recited in claim 7, wherein the first sensor and the second sensor comprise magnetic tunnel junctions.

9. The device recited in any one of claims 1 to 8, wherein the second material layer comprises diamond-like carbon.

10. The device recited in any one of claims 1 to 9, wherein the first material layer comprises a metal.

11. The device recited in claim 10, wherein the first material layer further comprises an insulator over the metal.

12. The device recited in claim 10 or claim 11, wherein the metal comprises gold.

13. The device recited in any one of claims 1 to 8, wherein: the first material layer comprises an oxide and the second material layer comprises diamond-like carbon, or the first material layer comprises a metal and the second material layer comprises an oxide.

14. The device recited in any one of claims 1 to 13, wherein a thickness of the first material layer over the first sensor is less than or equal to about 30 nanometers (nm).

15. The device recited in any one of claims 1 to 14, wherein the insulating material comprises an oxide.

16. A method of fabricating a device for sensing biomolecules, the method comprising: creating a plurality of capped sensors, the plurality of capped sensors comprising a plurality of sensors covered by respective caps of sacrificial material; encapsulating the plurality of capped sensors in an insulating material;Attorney Docket No. ROA-1004-WO / P39519-WO performing a planarizing procedure on a surface of the insulating material to expose the sacrificial material over each capped sensor of the plurality of capped sensors; removing the sacrificial material from each capped sensor of the plurality of capped sensors, thereby exposing top surfaces of the plurality of sensors; and applying a layer of a first material over the exposed top surfaces of the plurality of sensors.

17. The method of claim 16, further comprising: after applying the layer of the first material over the exposed top surfaces of the plurality of sensors, depositing a second material over a portion of the layer of the first material, wherein the portion of the layer of the first material is not situated over the plurality of sensors, and wherein a surface energy of the second material is lower than a surface energy of the first material.

18. The method of claim 17, wherein: the first material is hydrophilic; the second material is hydrophobic; or the first material is hydrophilic and the second material is hydrophobic.

19. The method of claim 17 or claim 18, wherein depositing the second material over the portion of the layer of the first material comprises at least one of chemical vapor deposition, physical vapor deposition (PVD), evaporation, sputtering, ion-beam deposition, pulsed laser deposition (PLD), atomic layer deposition (ALD), molecular beam epitaxy (MBE), electrodeposition, a solgel process, plasma-enhanced deposition (PECVD / PVD), spin coating, spray pyrolysis, electrophoretic deposition (EPD), or laser-assisted deposition.

20. The method of any one of claims 16 to 19, wherein creating the plurality of capped sensors comprises performing photolithography or electron-beam lithography (EBL).

21. The method of any one of claims 16 to 20, wherein creating the plurality of capped sensors comprises depositing a sacrificial layer over the plurality of sensors.

22. The method of claim 21, wherein the sacrificial material comprises diamond-like carbon (DLC) or parylene.Attorney Docket No. ROA-1004-WO / P39519-WO23. The method of claim 21 or claim 22, wherein depositing the sacrificial layer over the plurality of sensors comprises using at least one of chemical vapor deposition, physical vapor deposition (PVD), evaporation, sputtering, ion-beam deposition, pulsed laser deposition (PLD), atomic layer deposition (ALD), molecular beam epitaxy (MBE), electrodeposition, a sol-gel process, plasma-enhanced deposition (PECVD / PVD), spin coating, spray pyrolysis, electrophoretic deposition (EPD), or laser-assisted deposition.

24. The method of any one of claims 16 to 23, wherein creating the plurality of capped sensors comprises patterning the plurality of capped sensors.

25. The method of claim 24, wherein patterning the plurality of capped sensors comprises performing etching.

26. The method of any one of claims 16 to 25, wherein encapsulating the plurality of capped sensors in the insulating material comprises depositing the insulating material around each sensor of the plurality of capped sensors.

27. The method of claim 26, wherein encapsulating the plurality of capped sensors in the insulating material is performed using at least one of: chemical vapor deposition, physical vapor deposition (PVD), evaporation, sputtering, ion-beam deposition, pulsed laser deposition (PLD), atomic layer deposition (ALD), molecular beam epitaxy (MBE), electrodeposition, a sol-gel process, plasma-enhanced deposition (PECVD / PVD), spin coating, spray pyrolysis, electrophoretic deposition (EPD), or laser-assisted deposition.

28. The method of any one of claims 16 to 27, wherein performing the planarizing procedure on the surface of the insulating material to expose the sacrificial material over each sensor of the plurality of sensors comprises performing chemical mechanical polishing.

29. The method of any one of claims 16 to 28, wherein removing the sacrificial material comprises performing at least one of: selective wet chemistry, plasma etching, reactive ion etching (RIE), inductively coupled plasma etching, laser ablation, focused ion beam (FIB) etching, atomic layer etching (ALE), electrochemical etching, thermal etching, vapor phase etching, or ion implantation followed by selective etching.Attorney Docket No. ROA-1004-WO / P39519-WO30. The method of any one of claims 16 to 29, wherein applying the layer of the first material over the exposed top surfaces of the plurality of sensors comprises performing at least one of: chemical vapor deposition, physical vapor deposition (PVD), evaporation, sputtering, ion-beam deposition, pulsed laser deposition (PLD), atomic layer deposition (ALD), molecular beam epitaxy (MBE), electrodeposition, a sol-gel process, plasma-enhanced deposition (PECVD / PVD), spin coating, spray pyrolysis, electrophoretic deposition (EPD), or laser-assisted deposition..

31. The device for sensing molecules fabricated using the method recited in any one of claims 16 to 30.

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