Piezoresistive pressure sensor

Abstract

To provide a device having a piezoresistive pressure sensor.SOLUTION: A pressure sensor can have at least one diaphragm that is surrounded by at least a second diaphragm having a second thickness and has a first thickness, where the second thickness is larger than the first thickness. The at least one diaphragm can be composed of at least one irregular shape, and the at least one irregular shape includes two opposing, essentially round corner sections, and two opposing irregular corner sections. The irregular corner sections can have a projecting region including a piezo resistor. The opposing piezo resistor pairs can demarcate a Wheatstone bridge.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] FIELD OF THE DISCLOSURE Embodiments of the present disclosure generally relate to devices including piezoresistive pressure sensors. [Background technology]

[0002] Many different devices exist for detecting pressure in various media. In some instances, some of these devices are used in the medical field. Applicant has identified many technical challenges and difficulties associated with such devices for detecting air bubbles and / or blockages in fluids. Through exerted effort, ingenuity, and innovation, many of these identified problems have been solved by developing solutions included in embodiments of the present disclosure, many examples of which are described in detail herein. Summary of the Invention

[0003] Various exemplary embodiments described herein relate to devices that include piezoresistive pressure sensors.

[0004] According to various embodiments of the present disclosure, a device is provided. In some embodiments, the device comprises a pressure sensor. In some embodiments, the pressure sensor comprises at least one first diaphragm of a first thickness surrounded by at least one second diaphragm of a second thickness, the at least one second diaphragm being composed of two or more layers of material having thicknesses selected to achieve substantially zero effective stress, the second thickness being greater than the first thickness, and the at least one first diaphragm being composed of at least one irregular shape, the at least one irregular shape including two opposing substantially rounded corners and two opposing irregular corners, the two opposing irregular corners comprising protruding pointed regions comprising piezoresistors that define a Wheatstone bridge.

[0005] In some embodiments, the device further comprises four first diaphragms of the first thickness.

[0006] In some embodiments, the device further comprises four irregular shapes.

[0007] In some embodiments, the device further comprises a substrate defining a substantially round hole.

[0008] In some embodiments, the substrate is made of glass.

[0009] In some embodiments, opposing pairs of adjacent piezoresistors are configured to be displaced in either a first direction or a second direction based on an applied pressure, the first direction being opposite the second direction.

[0010] In some embodiments, the displacement defines a Wheatstone bridge configured to output a voltage proportional to the displacement of the piezoresistors.

[0011] According to various embodiments of the present disclosure, a pressure sensor is provided. In some embodiments, the pressure sensor comprises at least one first diaphragm of a first thickness surrounded by at least one second diaphragm of a second thickness, the at least one second diaphragm being composed of two or more layers of material having thicknesses selected to achieve substantially zero effective stress, the second thickness being greater than the first thickness, the at least one first diaphragm being composed of at least one irregular shape, the at least one irregular shape including two opposing substantially rounded corners and two opposing irregular corners, the two opposing irregular corners comprising protruding pointed regions comprising piezoresistors defining a Wheatstone bridge.

[0012] In some embodiments, the device further comprises four first diaphragms of the first thickness.

[0013] In some embodiments, the device further comprises four irregular shapes.

[0014] In some embodiments, the device further comprises a substrate defining a substantially round hole.

[0015] In some embodiments, the substrate is made of glass.

[0016] In some embodiments, opposing pairs of adjacent piezoresistors are configured to be displaced in either a first direction or a second direction based on an applied pressure, the first direction being opposite the second direction.

[0017] In some embodiments, the displacement defines a Wheatstone bridge configured to output a voltage proportional to the displacement of the piezoresistors.

[0018] According to various embodiments of the present disclosure, a system is provided. In some embodiments, the system includes a pressure sensor, the pressure sensor including at least one first diaphragm of a first thickness surrounded by at least one second diaphragm of a second thickness, the at least one second diaphragm being composed of two or more layers of material having a thickness selected to achieve substantially zero effective stress, the second thickness being greater than the first thickness, the at least one first diaphragm being composed of at least one irregular shape, the at least one irregular shape including two opposing substantially rounded corners and two opposing irregular corners, the two opposing irregular corners comprising protruding pointed regions comprising piezoresistors defining a Wheatstone bridge. In some embodiments, the system includes a device configured to receive information indicative of at least one pressure measured by the pressure sensor.

[0019] In some embodiments, the pressure sensor further comprises four first diaphragms of the first thickness.

[0020] In some embodiments, the pressure sensor further comprises four irregular squares.

[0021] In some embodiments, the pressure sensor further comprises a substrate defining a substantially circular hole, the substrate being positioned opposite the at least one first diaphragm.

[0022] In some embodiments, opposing pairs of adjacent piezoresistors are configured to be displaced in either a first direction or a second direction based on an applied pressure, the first direction being opposite the second direction.

[0023] In some embodiments, the displacement defines a Wheatstone bridge configured to output a voltage proportional to the displacement of the piezoresistors. [Brief explanation of the drawings]

[0024] The description of the illustrated embodiments may be read in conjunction with the accompanying figures. Unless otherwise noted, it will be understood that for simplicity and clarity of illustration, elements shown in the figures have not necessarily been drawn to scale. For example, unless otherwise noted, the dimensions of some of the elements may be exaggerated relative to other elements. Embodiments incorporating the teachings of the present disclosure are shown and described in connection with the figures presented herein. [Figure 1A] FIG. 1 is a perspective view of the "top" of a piezoresistive pressure sensor. [Figure 1B] FIG. 1 is a perspective view of the "bottom" of a piezoresistive pressure sensor. [Figure 2] 1 is a perspective view and an enlarged view of at least a portion of a piezoresistive pressure sensor; [Figure 3] 1A-1C are top and close-up views of piezoresistors of a piezoresistive pressure sensor according to some embodiments of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0025] Certain embodiments of the present disclosure will now be described in more detail below with reference to the accompanying drawings, in which some, but not all, embodiments of the present disclosure are shown. Indeed, these disclosures may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will satisfy applicable legal requirements. Like numbers refer to like elements throughout.

[0026] As used herein, terms such as "front," "rear," "top," "bottom," "left," "right," etc. are used for explanatory purposes to describe the relative positions of particular components or portions of components in the examples provided below. Additionally, as will be apparent to those skilled in the art in view of this disclosure, the terms "substantially" and "approximately" indicate that the referenced element or associated description is accurate to within applicable engineering tolerances.

[0027] As used herein, the term "comprising" means including, but not limited to, and should be interpreted as typically used in patent contexts. The use of broader terms such as "comprises," "includes," and "having" should be understood to support narrower terms such as "consisting of," "consisting essentially of," and "comprised substantially of."

[0028] The phrases "in one embodiment," "according to one embodiment," "in some embodiments," and similar phrases generally mean that the particular feature, structure, or characteristic that follows the phrase may be included in at least one embodiment of the present disclosure, and may be included in more than one embodiment of the present disclosure (importantly, such phrases do not necessarily refer to the same embodiment).

[0029] The phrases "in one embodiment," "according to one embodiment," "in some embodiments," and similar phrases generally mean that the particular feature, structure, or characteristic that follows the phrase may be included in at least one embodiment of the present disclosure, and may be included in more than one embodiment of the present disclosure (importantly, such phrases do not necessarily refer to the same embodiment).

[0030] When a component or feature is described herein as being included or having a characteristic and "may," "can," "could," "should," "would," "preferably," "possibly," "typically," "optionally," "for example," "in one embodiment," "in some embodiments," "in many cases," or "might" (or other such phrases), that particular component or feature is not required to be included or have that characteristic. Such component or feature may be optionally included in or excluded from some embodiments.

[0031] As used herein, the word "example" or "exemplary" means "serving as an example, instance, or illustration." Any embodiment described herein as "example" or "exemplary" is not necessarily to be construed as preferred or advantageous over other embodiments.

[0032] The terms "electrically coupled," "electrically coupled," "electrically coupled," "electrically connected," "electrically connecting," "electrically connecting," "communicate," or "electronically communicate" in this disclosure refer to two or more elements or components that are connected via wired and / or wireless means such that signals, voltage / current, data and / or information can be sent to and / or received from those elements or components.

[0033] In this disclosure, the term "in fluid communication with" refers to two or more elements or components that are connected via one or more pathways or passages such that a fluid or other flow medium can enter and / or exit those elements or components.

[0034] The term "component" may refer to an article, device, or apparatus that may comprise one or more surfaces, portions, layers, and / or elements. For example, an exemplary component may comprise one or more substrates that may provide an underlying layer for the component, may form part of a substrate, and / or may comprise one or more elements disposed on a substrate. In this disclosure, the term "element" may refer to an article, device, or apparatus that may provide one or more functions.

[0035] The term "sensor" refers to a component that can detect, measure, and / or determine one or more attributes or characteristics of an environment or medium, including, but not limited to, pressure.

[0036] In some instances, conventional pressure sensors and their fabrication are limited by various characteristics. For example, fabricating pressure sensors with very thin diaphragms (e.g., on the order of a few microns in thickness) is difficult using conventional methods. In some instances, conventional pressure sensors have a large initial voltage offset even when no pressure is applied.

[0037] Embodiments of the present disclosure provide, in some examples, devices comprising piezoresistive pressure sensors, and in some examples, devices comprising piezoresistive ultrasensitive pressure sensors.

[0038] Exemplary embodiments of the devices described herein may include a device comprising a pressure sensor. Exemplary embodiments of the devices described herein may include a pressure sensor comprising at least one first diaphragm of a first thickness surrounded by at least one second diaphragm of a second thickness, the at least one second diaphragm being composed of two or more layers of material having thicknesses selected to achieve substantially zero effective stress, the second thickness being greater than the first thickness. In some examples, the at least one diaphragm is composed of at least one irregular shape (e.g., an irregular square, an irregular rectangle, and / or other shape), the at least one irregular shape including two opposing substantially rounded corners and two opposing irregular corners, the two opposing irregular corners comprising protruding pointed regions. In some examples, the protruding pointed regions comprise piezoresistors, the opposing pairs of piezoresistors defining a Wheatstone bridge.

[0039] Exemplary embodiments of the present disclosure provide pressure sensors and / or devices including such pressure sensors, in some examples, having one or more first diaphragms of a first thickness and one or more second diaphragms of a second thickness (e.g., peripheral regions, connecting beams, and / or peripheral edges, etc.), the second thickness being greater than the first thickness. In some examples, the one or more second diaphragms are comprised of two or more layers of material having thicknesses selected to achieve substantially zero effective stress. In some examples, the diaphragms are thin (e.g., 5 microns, 5 microns or less, 3 microns or less, etc.). In some examples, the one or more second diaphragms are thin and / or thicker than the first diaphragm (e.g., 10 microns, 10 microns or less, 6 microns or less, etc.). In some examples, the diaphragms are irregularly shaped (e.g., irregular squares, irregular rectangles, and / or other shapes) with piezoresistors on half or two of their corners. Exemplary embodiments of the present disclosure provide, in some examples, a piezoresistive pressure sensor, as described above. Such piezoresistive pressure sensors may, in some examples, be used in medical applications. For example, such piezoresistive pressure sensors may detect pressures exerted by water, such as, for example, one inch of water, one inch or less of water (e.g., pressures on the order of 250 Pa, 250 Pa, less than 250 Pa, more than 250 Pa, etc.).

[0040] As described herein, embodiments of the present disclosure, in some examples, provide devices for determining pressure of various media. Embodiments of the present disclosure, in some examples, provide ultra-sensitive pressure sensors that are more sensitive than conventional pressure sensors. Embodiments of the present disclosure, in some examples, provide pressure sensors that have a nearly negligible initial voltage offset (e.g., in the absence of applied and / or detected pressure, the pressure sensor outputs a nearly zero voltage).

[0041] To address challenges and limitations associated with devices for determining pressure of various media, various examples of the present disclosure may provide example devices, associated sensors, and associated methods for sensing pressure.

[0042] 1A-1B are perspective views of a piezoresistive pressure sensor. Referring now to FIG. 1A, a perspective view of the "top" of piezoresistive pressure sensor 100 is provided. Piezoresistive pressure sensor 100 may be an ultra-sensitive piezoresistive pressure sensor. Piezoresistive pressure sensor 100 comprises at least one first diaphragm 102, at least one second diaphragm 104, at least one electrical contact 106, and / or a substrate 108 (further described with respect to FIG. 1B). The "top" may be defined as the surface having at least one diaphragm 102, with at least one diaphragm exposed. The "bottom" may be defined as the surface having the substrate 108.

[0043] The piezoresistive pressure sensor 100 may include at least one first diaphragm 102 of a first thickness surrounded by at least one second diaphragm 104 of a second thickness (e.g., including a region of the second thickness, the second thickness being greater than the first thickness). The at least one second diaphragm 104 may be comprised of two or more layers of material having thicknesses selected to achieve substantially zero effective stress. The at least one first diaphragm 102 may be comprised of at least one irregular shape, the at least one irregular shape including two opposing substantially rounded corners and two opposing irregular corners, the irregular corners comprising protruding, pointed regions. The protruding, pointed regions of the at least one first diaphragm 102 may comprise piezoresistors. Opposing pairs of piezoresistors can define a Wheatstone bridge, whereby, when pressure is applied, two opposing piezoresistors can be displaced in a first direction and two opposing piezoresistors can be displaced in a second direction, opposite the first direction, to generate an output voltage.

[0044] In some examples, the at least one first diaphragm 102 comprises four diaphragms (e.g., as shown in FIG. 1A ). In some examples, the four diaphragms are comprised of irregular shapes (e.g., irregular squares, irregular rectangles, and / or other shapes). The irregular shapes may have two opposing substantially rounded corners and two opposing irregular corners. In some examples, each of the four diaphragms comprises a pair of opposing irregular corners with protruding, pointed regions. The protruding, pointed regions may comprise high-stress piezoresistors. For example, when a pressure differential is sensed by the pressure sensor (e.g., the “top” and “bottom” surfaces of the pressure sensor sense different pressures), each pair of adjacent irregular corners is displaced in either a first direction or a second direction (e.g., opposing pairs of irregular corners are displaced in the same direction as each other). This displacement forms a Wheatstone bridge, which outputs a voltage proportional to the displacement of the piezoresistors.

[0045] At least one diaphragm 102 may be composed of bare silicon. At least one first diaphragm 102 may be substantially free of an oxide film (e.g., that may be deposited during the manufacturing process). At least one diaphragm 102 may have a first thickness. At least one second diaphragm 104 may have a second thickness. The second thickness may be greater than the first thickness. For example, the first thickness may be approximately 3-5 microns (e.g., 5 microns, 5 microns or less, 3 microns, etc.) and / or the second thickness may be approximately 6-10 microns (e.g., 10 microns, 10 microns or less, 6 microns, etc.).

[0046] In some examples, the at least one second diaphragm 104 is comprised of one or more layers. In some examples, the at least one second diaphragm 104 is comprised of two or more layers. In some examples, the at least one second diaphragm 104 is comprised of a first layer of silicon including a piezoresistive region, a layer of oxide, and / or a second layer of silicon, where the second layer of silicon is thicker than the first layer of silicon. In some examples, the at least one second diaphragm 104 is comprised of a silicon oxide / silicon nitride stack, where the silicon oxide layer has compressive stress and the silicon nitride layer has tensile stress. By selecting predetermined thicknesses of the silicon oxide and / or silicon nitride, a nearly zero "effective stress" can be achieved within the stack. In some examples, the at least one second diaphragm 104 is comprised of a silicon oxide / polysilicon / silicon nitride stack, where the polysilicon (e.g., doped polysilicon) functions as an electric field protection plate. The thickness of the silicon oxide, polysilicon, and / or silicon nitride may be selected to provide a near-zero "effective stress" in the silicon substrate. In some examples, the at least one second diaphragm 104 comprises a region that surrounds the irregular shape of the at least one diaphragm 102.

[0047] In some examples, the at least one electrical contact 106 is a metal contact. For example, the at least one electrical contact 106 may be composed of a first layer of titanium tungsten (TiW) and / or a layer of gold (Au) to form at least one TiW / Au contact. In some examples, the at least one electrical contact 106 is used to transmit pressure data from the pressure sensor to at least one other device.

[0048] In some examples, a device may include a pressure sensor, such as piezoresistive pressure sensor 100. Apparatus including piezoresistive pressure sensors may be used in medical applications to sense the pressure of various media, such as fluids.

[0049] 1B, a perspective view of the "bottom" of the piezoresistive pressure sensor 100 is provided. The piezoresistive pressure sensor 100 includes a substrate 108. The substrate 108 may be comprised of a substrate (e.g., a plate and / or other object). The substrate may be comprised of glass, silicon, a material having a thermal expansion coefficient substantially similar to that of silicon, and / or other materials. The substrate 108 may define, for example, a substantially round hole located approximately in the center of the substrate 108. The substrate 108 may be disposed opposite at least one first diaphragm. The substantially round hole in the substrate 108 may expose the "bottom" of the piezoresistive pressure sensor 100 to a "reference pressure" (e.g., a pressure outside the pressure sensor, such as ambient pressure).

[0050] The piezoresistive pressure sensor 100 may be configured in a system further including another device configured to receive information indicative of at least one pressure measured by the piezoresistive pressure sensor 100. The other device may be coupled to the piezoresistive pressure sensor 100 via at least one electrical contact 106 (e.g., via wire bonding to the at least one electrical contact 106).

[0051] Referring now to FIG. 2, a perspective view and an enlarged view of at least a portion of a piezoresistive pressure sensor are provided. FIG. 2 shows a perspective view 200 of a piezoresistive pressure sensor. The piezoresistive pressure sensor of FIG. 200 may be the piezoresistive pressure sensor 100. The enlarged view of at least a portion of the piezoresistive pressure sensor, for example, shows a cross section of at least one second diaphragm 104. The cross section of the at least one second diaphragm 104 includes a silicon oxide / silicon nitride stack, where the silicon oxide layer is designated by reference numeral 204 and the silicon nitride layer is designated by reference numeral 202. The silicon nitride layer 202 (e.g., silicon nitride) may have a tensile stress. The silicon oxide layer 204 (e.g., silicon oxide) may have a compressive stress. In combination, the silicon oxide / silicon nitride stack may have an "effective stress" of approximately zero. A cross-section of the at least one second diaphragm 104 can include two or more layers, such as, for example, a silicon oxide / polysilicon / silicon nitride stack, where the polysilicon (e.g., doped polysilicon) acts as a field protection plate. The thicknesses of the silicon oxide, polysilicon, and / or silicon nitride can be selected to provide a near-zero "effective stress" in the silicon substrate.

[0052] Referring now to FIG. 3 , top and enlarged views of piezoresistors of a piezoresistive pressure sensor are provided. Now, referring to the top-down view 300, assume that pairs of irregular corners in the image can be described as “top,” “bottom,” “left,” and “right” according to their orientation in the exemplary image. The upper and lower piezoresistors can be substantially parallel to the edges of the at least one diaphragm 102. The left and right piezoresistors can be substantially perpendicular to the edges of the at least one diaphragm 102. Enlarged view 302 shows how the upper (and / or lower) piezoresistors can be substantially parallel to the edges of the at least one diaphragm 102. Enlarged view 304 shows how the right (and / or left) piezoresistors can be substantially perpendicular to the edges of the at least one diaphragm 102. The piezoresistors can be lightly doped p-type piezoresistors. Lightly doped p-type piezoresistors are essentially <110> The silicon of the at least one diaphragm 102 may be substantially <110> It could be in the direction.

[0053] The operations and processes described herein support combinations of means for performing the specified functions and combinations of operations for performing the specified functions. It will be understood that one or more operations and combinations of operations may be implemented by a dedicated hardware-based computer system that performs the specified functions, or a combination of dedicated hardware and computer instructions.

[0054] In some exemplary embodiments, certain of the operations herein may be modified or further extended as described below. Furthermore, in some embodiments, additional optional operations may also be included. It should be understood that each of the modifications, optional additions, or extensions described herein may be included with the operations herein, either alone or in combination with any other of the features described herein.

[0055] The foregoing method and process descriptions are provided merely as examples and are not intended to require or imply that the steps of the various embodiments must be performed in the order presented. As will be understood by one of ordinary skill in the art, the order of steps in the foregoing embodiments may be performed in any order. Words such as "then," "then," "next," and similar words are not intended to limit the order of the steps. These words are merely used to guide the reader through the method descriptions. Furthermore, any reference to claim elements in the singular, for example, using the articles "a," "an," or "the," should not be construed as limiting the element to the singular but may, in some cases, be construed in the plural.

[0056] While various embodiments according to the principles disclosed herein have been shown and described above, modifications thereof can be made by those skilled in the art without departing from the teachings of the present disclosure. The embodiments described herein are merely representative and are not intended to be limiting. Many variations, combinations, and modifications are possible and fall within the scope of the present disclosure. Alternative embodiments resulting from combining, integrating, and / or omitting features of the embodiments are also within the scope of the present disclosure. Accordingly, the scope of protection is not limited by the above description, but is defined by the claims that follow, including all equivalents of the subject matter of the claims. Each and every claim is incorporated herein as further disclosure, and the claims are embodiments of the present disclosure. Furthermore, while any advantages and features described above may relate to particular embodiments, application of such issued claims is not limited to processes and structures achieving any or all of the above advantages or having any or all of the above features.

[0057] Additionally, the section headings used herein are provided to conform to the proposition under Title 37, Code of Federal Regulations, Section 1.77, or to otherwise provide organizational guidance. These headings do not limit or characterize the disclosure set forth in any claims that may issue from this disclosure. For example, the description of a technology in the "Background" section should not be construed as an admission that a particular technology is prior art to any disclosure in this disclosure. The "Summary" section should also not be considered a limiting feature of the disclosure that will be set forth in the claims to be issued. Furthermore, any reference in this disclosure to the singular "disclosure" or "embodiments" should not be used to assert a single point of novelty in the disclosure. Multiple embodiments of the disclosure may be set forth according to the limitations of the multiple claims that issue from this disclosure, and such claims therefore define the disclosure and their equivalents protected thereby. In all cases, the scope of the claims should be considered on their own merits in light of this disclosure, but should not be constrained by the headings set forth herein.

[0058] Additionally, the systems, subsystems, devices, techniques, and methods described and illustrated in various embodiments, individually or separately, may be combined or integrated with other systems, modules, techniques, or methods without departing from the scope of the present disclosure. Other devices or components shown or described as coupled or in communication with each other may be indirectly coupled through some intermediate device or component, whether electrical, mechanical, or otherwise. Other examples of changes, substitutions, and alterations will be ascertainable by those skilled in the art and may be made without departing from the scope disclosed herein.

[0059] Many modifications and other embodiments of the disclosure described herein will come to mind to one skilled in the art to which these embodiments pertain having the benefit of the teachings presented in the foregoing descriptions and the associated figures. While the figures illustrate only certain components of the devices and systems described herein, various other components may be used in conjunction with the components and structures disclosed herein. It is to be understood, therefore, that the disclosure is not limited to the particular embodiments disclosed, and that modifications and other embodiments are intended to be included within the scope of the appended claims. For example, various elements or components may be combined, rearranged, or integrated in another system, or certain features may be omitted, or not implemented. Moreover, the steps in any method described above need not necessarily occur in the order depicted in the accompanying figures; in some cases, one or more of the depicted steps may occur substantially concurrently or may involve additional steps. Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.

Claims

1. A device, A pressure sensor, the pressure sensor comprising: a pressure sensor comprising at least one first diaphragm of a first thickness surrounded by at least one second diaphragm of a second thickness, said at least one second diaphragm being constructed from two or more layers of material having thicknesses selected to achieve substantially zero effective stress, said second thickness being greater than said first thickness; the at least one first diaphragm is comprised of at least one irregular shape, the at least one irregular shape including two opposing substantially rounded corners and two opposing irregular corners, the two opposing irregular corners comprising protruding pointed regions containing piezoresistors that define a Wheatstone bridge.

2. at least, four first diaphragms of said first thickness; Four irregular squares, or The device of claim 1 , further comprising a substrate defining a substantially circular hole, said substrate disposed opposite said at least one first diaphragm.

3. 2. The device of claim 1, wherein opposing pairs of adjacent piezoresistors are configured to be displaced in either a first direction or a second direction based on an applied pressure, the first direction being opposite the second direction, and the displacements define the Wheatstone bridge configured to output a voltage proportional to the displacement of the piezoresistors.

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