Biometric authentication sensors containing oxide semiconductors, biometric authentication sensors for display devices, and methods for manufacturing and using the same.

Abstract

The present invention provides sensors, devices, systems, and methods for biometric authentication. Such a device or system comprises a microheater and at least a microtemperature sensor for active thermal sensing, the microtemperature sensor may include an oxide semiconductor material. The microheater and microtemperature sensor may be arranged separately or integrated into a single pixel. The present disclosure provides out-cell or in-cell biometric sensors for display devices, such as out-cell or in-cell fingerprint sensors for fingerprint-on-display (FoD) devices. The pixel for active thermal sensing includes an oxide semiconductor material. Furthermore, the present invention also provides methods for manufacturing and using the sensors, devices, or systems.

Description

Technical Field

[0001] Priority Claim and Cross - Reference This application claims the benefit of U.S. Provisional Application No. 63 / 647,208, filed on May 14, 2024, which is hereby incorporated by reference in its entirety.

[0002] This disclosure relates to an apparatus or method for measuring a biometric pattern. More specifically, the disclosed subject matter relates to an apparatus or system for display and biometric sensing, such as a fingerprint sensor, and a method for measuring or obtaining an image of a biometric (e.g., fingerprint) pattern.

Background Art

[0003] Biometric sensors, such as fingerprint sensors, are one form of technology used to provide biometric security. The fine patterns formed by ridges and valleys on the skin of a finger can be mapped by sensing arrays with fundamentally different operating principles. Some sensors utilize thermal signals, while others utilize electrical, pressure, or optical signals. Active sensors quantify specific physical parameters in response to a given stimulus. The level of accuracy is limited by the physical principles used to read the fingerprint pattern. Additionally, resistance to environmental variables, such as dirt or humidity, is also important when performing a fingerprint scan.

Summary of the Invention

Problems to be Solved by the Invention

[0004] Fingerprint sensors are frequently used in electronic devices to verify the user's identity and restrict access unless the sensor confirms that an authorized user is attempting to use the device. For example, certain smart credit cards require user authentication via a fingerprint sensor before use. Fingerprint sensors are also incorporated into computer devices such as smartphones, tablet computers, laptop computers, and POS terminals, ensuring that only authorized users can unlock and use such devices. [Means for solving the problem]

[0005] This disclosure provides sensors, devices, systems, and methods for biometric authentication. According to some embodiments, such devices or systems have a microheater and a microtemperature sensor, which may include an oxide semiconductor material. According to some embodiments, this disclosure provides This specification provides out-cell or in-cell biometric sensor-on-display devices, such as the out-cell or in-cell fingerprint-on-display (FoD) device described herein. The thermal sensing pixels include oxide semiconductor materials described herein. Methods for manufacturing and using the sensors, devices, and systems are also provided.

[0006] In one embodiment, the disclosure provides a sensor for biometric authentication, an apparatus including a sensor for biometric authentication, and a system comprising a sensor for biometric authentication. The sensor comprises a pixel matrix having a plurality of pixels configured to measure a biometric pattern. The sensor further comprises a micro-temperature sensor and a micro-heater disposed within each pixel. The micro-temperature sensor comprises an oxide semiconductor material. The micro-heater may comprise an oxide semiconductor material, a metal and a conductive material such as a transparent conductive oxide (TCO), or a combination thereof. The plurality of pixels comprises thermal sensing pixels configured to operate on at least an active thermal sensing principle, wherein a low-power thermal pulse is applied to the thermal sensing pixel and a response corresponding to the biometric pattern is measured. In the disclosure, active thermal sensing may be combined with passive thermal sensing or other modes.

[0007] In some embodiments, the oxide semiconductor material includes indium gallium zinc oxide (IGZO) or modified IGZO as described herein. Modified IGZO contains elements such as aluminum (Al), tin (Sn), titanium (Ti), tungsten (Ta), zirconium (Zr), cobalt (Co), nickel (Ni), hafnium (Hf), silicon (Si), fluorine (F), germanium (Ge), yttrium (Y), radium (La), and any combination thereof. IGZO or modified IGZO can be amorphous or crystalline. The oxide semiconductor material may have a suitable temperature coefficient, for example, in the range of -2 mV / °C to -200 mV / °C or any other range described herein. The oxide semiconductor material may have a suitable sheet resistance, for example, in the range of 5 kΩ / sq to 3 MΩ / sq or any other range described herein. The oxide semiconductor material may have good transparency as described herein.

[0008] Each of the micro-temperature sensors and micro-heaters is either a thin-film transistor (TFT), diode, or thermistor.

[0009] In some embodiments, the micro-temperature sensor and micro-heater are integrated into a single device at each pixel. In some embodiments, the micro-temperature sensor and micro-heater are separated at each pixel, and the micro-heater is part of a plurality of micro-heater lines. The micro-heater may be made of metal.

[0010] In some embodiments, the sensor further comprises a capacitive touch sensing element that is self-capacitive or mutually capacitive and is active-matrix or passive-matrix. For example, in some embodiments, the capacitive touch sensing element is a passive-matrix mutually capacitive touch sensor or an active-matrix self-capacitive touch sensor.

[0011] This sensor has excellent anti-spoofing performance. For example, in some embodiments, the capacitive touch sensing element is an active-matrix self-capacitive touch sensor used in combination with active thermal sensing to improve anti-spoofing performance. As another example, the thermal sensing pixel comprises a pixel that performs passive thermal sensing in combination with active thermal sensing to improve anti-spoofing performance.

[0012] In other embodiments, the Disclosure provides apparatus comprising such sensors and systems comprising the sensors described herein. The Disclosure also provides a method for manufacturing such sensors. The method comprises forming a pixel matrix having a plurality of pixels, each having a microtemperature sensor and a microheater.

[0013] In another embodiment, the Disclosure provides a biometric sensor on-display device (or system), such as an on-display (FoD) device. Such a device or system comprises a display layer, a sensor substrate disposed on the display layer, and a sensor layer disposed on the sensor substrate and comprising a pixel matrix. The pixel matrix has a plurality of pixels configured to measure a biometric pattern. The plurality of pixels comprises capacitive touch sensing elements and thermal sensing pixels configured to operate on at least an active thermal sensing principle, wherein a low-power thermal pulse is applied to the thermal sensing pixels and a response corresponding to the biometric pattern is measured.

[0014] Capacitive touch sensing elements are either self-capacitive or mutually capacitive. Capacitive touch sensing elements are either active-matrix or passive-matrix.

[0015] Capacitive touch sensing elements are passive matrix mutual capacitive touch sensors or active matrix self-capacitive touch sensors. Thermal sensing pixels include oxide semiconductor materials. In some embodiments, the oxide semiconductor material includes indium gallium zinc oxide (IGZO) or modified IGZO as described herein. Each thermal sensing pixel comprises a thin-film transistor (TFT), a diode, or a thermistor, or a combination thereof.

[0016] In some embodiments, the device further comprises a transparent hard coat placed on top of the sensing layer.

[0017] In some embodiments, the apparatus further includes an optically transparent adhesive placed between the sensor substrate and the display layer.

[0018] In some embodiments, the device is an out-cell type fingerprint sensor for a fingerprint-on-display (FoD) device.

[0019] This device has excellent anti-spoofing performance. For example, in some embodiments, the capacitive touch sensing element is an active-matrix self-capacitive touch sensor used in combination with active thermal sensing to improve anti-spoofing performance. In another example, the thermal sensing pixel comprises a pixel that performs passive thermal sensing in combination with active thermal sensing to improve anti-spoofing performance.

[0020] In another embodiment, the disclosure provides a biometric sensor device for a display, comprising a substrate, a display layer disposed on the substrate, and a sensor layer disposed within the display layer. The display layer comprises a plurality of display pixels. The sensor layer comprises a pixel matrix. The pixel matrix has a plurality of sensing pixels configured to measure a biometric pattern. The plurality of pixels have capacitive touch sensing elements. The thermal sensing pixels are configured to operate on at least an active thermal sensing principle, wherein a low-power thermal pulse is applied to the thermal sensing pixels and a response corresponding to the biometric pattern is measured.

[0021] Capacitive touch sensing elements are either self-capacitive or mutually capacitive. Capacitive touch sensing elements are either active-matrix or passive-matrix.

[0022] In some embodiments, the capacitive touch sensing element is a passive-matrix mutual-capacitive touch sensor or an active-matrix self-capacitive touch sensor, and the thermal sensing pixel comprises an oxide semiconductor material. In some embodiments, the oxide semiconductor material comprises indium gallium zinc oxide (IGZO) or modified IGZO as described herein. Each thermal sensing pixel comprises a thin-film transistor (TFT), a diode, or a thermistor, or a combination thereof.

[0023] In some embodiments, the apparatus further comprises a transparent hard coat placed on top of the display layer.

[0024] In some embodiments, the device is an in-cell type fingerprint on display (FoD) device.

[0025] The device has excellent anti-spoofing performance. For example, in some embodiments, the capacitive touch sensing element is an active matrix self-capacitance touch sensor used in combination with active thermal sensing to improve anti-spoofing performance. As another example, the thermal sensing pixels include pixels that perform passive thermal sensing in combination with active thermal sensing to improve anti-spoofing performance.

[0026] In another aspect, the present disclosure provides a system comprising any sensor or device described herein.

[0027] In another aspect, the present disclosure provides a method of manufacturing a sensor, device or system described herein.

[0028] In the products and methods described herein, the biometric pattern is, in some embodiments, a fingerprint or a palm pattern.

[0029] In another aspect, the present disclosure provides a method of using any of the sensors, devices or systems described herein. The method comprises the step of measuring or acquiring an image of a biometric pattern of a subject. In some embodiments, the biometric pattern is a fingerprint or a palm pattern. The sensor has anti-spoofing performance characterized by extremely low false rejection rate (FRR) and false acceptance rate (FAR). For example, the FRR is less than 1%, and the FAR is less than 0.001%, for example, less than 1 ppm. The FRR and FAR can be set to any other range described herein.

Brief Description of the Drawings

[0030] This disclosure is best understood when read in conjunction with the accompanying drawings. Following common practice, it is emphasized that various features in the drawings are not necessarily to scale. Rather, the dimensions of various features have been arbitrarily enlarged or reduced for clarity. Similar reference numerals indicate similar features throughout the specification and drawings.

[0031] [Figure 1A] Figure 1A is a cross-sectional view showing an example of a fingerprint sensor array (Configuration 1) in which a micro-temperature sensor and a micro-heater are incorporated into each of several embodiments.

[0032] [Figure 1B] Figure 1B is a top view showing three exemplary rows of the fingerprint sensor array shown in Figure 1A.

[0033] [Figure 2A] Figure 2A is a cross-sectional view showing an example of a fingerprint sensor array (Configuration 2) having separate micro-temperature sensors and micro-heater lines according to several embodiments.

[0034] [Figure 2B] Figure 2B is a top view showing three exemplary rows of the fingerprint sensor array shown in Figure 2A.

[0035] [Figure 3] Figure 3 is a cross-sectional view showing an exemplary device having a fingerprint-on-display (FoD) structure based on a capacitive touch sensor and an active thermal fingerprint sensor according to several embodiments.

[0036] [Figure 4A] Figure 4A is a plan view showing an example (Scenario 1) of the exemplary apparatus shown in Figure 3, which has a coarse grid passive matrix mutual capacitive touch sensor and a dense grid active matrix fingerprint sensor according to several embodiments. Figure 4A is a top view of the example (Scenario 1) of the apparatus in Figure 3 as seen through a transparent hard coat.

[0037] [Figure 4B] Figure 4B is a plan view showing another example (Scenario 2) of the exemplary apparatus of Figure 3, which has a dense grid active matrix self-capacitive touch sensor and fingerprint sensor, as well as a dense grid active matrix fingerprint sensor, according to several embodiments. Figure 4B is a top view of an example (Scenario 2) of the apparatus of Figure 3 as seen through a transparent hard coat.

[0038] [Figure 5] Figure 5 is a cross-sectional view of an exemplary apparatus having an out-cell FoD structure based on an active matrix self-capacitive touch sensor and an active thermal fingerprint sensor according to several embodiments.

[0039] [Figure 6] Figure 6 shows an example of the exemplary apparatus shown in Figure 5, which has a coarse grid active matrix self-capacitive touch sensor and a dense grid active thermal fingerprint sensor, according to several embodiments (viewed from the top view of Figure 5 through a transparent hard coat).

[0040] [Figure 7A] Figure 7A is a cross-sectional view of an exemplary apparatus having an in-cell type side-by-side top-emitting OLED or microLED with a coarse grid mutual capacitance touch sensor and a dense grid active thermal fingerprint sensor according to several embodiments.

[0041] [Figure 7B] Figure 7B is a plan (top) view showing a sub-row of the sensor array of an exemplary device from Figure 7A, illustrating the density of light-emitting pixels, mutually capacitive touch pixels, and active thermal sensing pixels according to several embodiments.

[0042] [Figure 8A-8B]Figures 8A and 8B show exemplary devices having an in-cell type side-by-side top-emitting OLED or microLED with a dense grid active matrix self-capacitive touch sensor and an active thermal fingerprint sensor. Figure 8A is a cross-sectional view showing the sensor array. Figure 8B is a top plan view showing a partial row of the sensor array.

[0043] [Figures 9A-9C] Figures 9A to 9C show size and resolution configurable capacitive and thermal scan steps according to several embodiments.

[0044] [Figure 10A-10D] Figures 10A to 10D show four exemplary thin-film transistor (TFT) device structures having channels containing oxide semiconductor materials used in exemplary devices having active thermal fingerprint sensors according to several embodiments. [Modes for carrying out the invention]

[0045] This description of the embodiment is intended to be read in conjunction with the accompanying drawings, which are considered to be part of the entire specification. In the specification, “lower,” “upper,” “horizontal,” “vertical,” “up,” “down,” “upward,” “downward,” “upper side,” “lower side,” and their derivatives (e.g., “horizontally,” “downward,” “upward,” etc.) should be interpreted as referring to the direction being described at that time or the direction shown in the drawings. These relative terms are for illustrative purposes only and do not require the device to be constructed or operate in a particular orientation. Terms relating to mounting, coupling, etc., such as “connected” and “interconnected,” refer to both movable and rigid mounting or relationships, as well as relationships in which structures are fixed or mounted to each other directly or indirectly through intervening structures, unless otherwise specified.

[0046] For the purposes of later explanation, it should be understood that the embodiments described below may envision alternative modifications and embodiments. It should also be understood that the specific articles, compositions, and / or processes described herein are illustrative and should not be constrained.

[0047] In this specification, unless the context clearly indicates otherwise, singular nouns “a,” “an,” and “the” include plural nouns, and references to specific numbers include at least that specific number. When a value is expressed as an approximation using the preceding term “about,” it should be understood that the specific number forms another embodiment. In this specification, “about X” (in which case X is a number) preferably refers to ±10% of the comprehensively stated value. For example, the expression “about 8” preferably refers comprehensively to values ​​from 7.2 to 8.8. Where present, all ranges are comprehensive and combinable. For example, if the range “1 to 5” is stated, it should be interpreted that the stated range includes ranges such as “1 to 4,” “1 to 3,” “1 to 2,” “1 to 2 and 4 to 5,” “1 to 3 and 5,” “2 to 5,” etc. Furthermore, if a list of options is provided positively, such a list can be interpreted as meaning that any of the options may be excluded, for example, by a negative limitation in the claims. For example, if a range of "1 to 5" is described, the described range may be interpreted to include situations in which any of 1, 2, 3, 4, or 5 is negatively excluded. Thus, the description "1 to 5" may be interpreted as "including 1 and 3 to 5 but not 2" or simply "not 2". Any component, element, attribute, or step described positively in this specification is intended to be expressly excluded in the claims, regardless of whether it is listed as an alternative or described independently.

[0048] Unless otherwise specified, the terms “connected” or “coupled” as used herein are understood to include various connections or couplings between components. In some embodiments, the connections or couplings are provided for transmitting signals for conducting electricity or for communication. Such connections or couplings can be made via wired, wireless, or cloud-based methods.

[0049] As used herein, the term “biometric sensor” refers to a sensor for detecting, capturing, and / or measuring the unique biological characteristics and patterns of a human-like subject for identification and authentication. In some embodiments, the biometric pattern refers to a pattern of skin on a part of the body of a human-like subject, including, but not limited to, fingerprints or palm prints. Biometric sensors are also called fingerprint sensors or palm print sensors. A biometric sensor comprises a pixel array which may have microheaters and / or microtemperature sensors. When a biometric sensor operates on a thermal principle, in this disclosure it may operate on an active thermal principle or a combination of the active and passive thermal principles.

[0050] The principles of "active thermal" and "passive thermal" are distinguished based on whether or not heat is applied to the biometric sensor, for example, whether or not it is applied via a microheater in the array of biometric sensors.

[0051] For example, when a biometric sensor, such as a fingerprint sensor, is configured to operate on the principle of "passive thermal sensing," such a sensor comprises an array of pixels, each equipped with a micro-temperature sensor based solely on a thin-film device, which maps the fingerprint image based on minute temperature differences in the sensor surface area corresponding to the "valley" and "ridge" regions of the fingerprint. Microheaters are absent or not turned on. Ridges are raised lines on the skin, such as the skin of a fingertip, and valleys are depressions between ridges.

[0052] In various embodiments, biometric sensors, such as the fingerprint sensor of this disclosure, operate on an active thermal sensing principle. In such embodiments, a low-power thermal pulse is applied to each sensor pixel for a short period, and the response is measured. Based on the active thermal sensing principle, the active thermal sensor measures the thermal conductivity of an object to a given heating stimulus. Examples of active thermal sensing principles suitable for biometric sensors, such as the fingerprint sensor of this disclosure, are disclosed in U.S. Patent No. 6,091,837 by Dinh, titled “Sensor for Acquiring Fingerprint Images Based on Heat Transfer,” and U.S. Patent No. 8,724,860 by Dinh, titled “Apparatus for Fingerprint Sensing and Other Measurements,” the entirety of these patent specifications are incorporated herein by reference. U.S. Patent No. 6,091,837 describes fingerprint sensing, and such a principle may be used in other biometric sensors of this disclosure. The response to a stimulus is measured by each of the sensing sites in the sensor array. The thermal response of an element depends in part on the stimulus provided; that is, the response increases as the stimulus increases. The detection site is heated by applying an electric current to the site. A low-power pulse may also be applied by a microheater in the pixel of the biometric sensor.

[0053] The thermal sensor principle utilizes a heat transfer mechanism to distinguish between the valleys and ridges of a fingerprint. This is because the skin structure has different heat transfer characteristics. A short thermal pulse is applied to a selected pixel of the sensor array (or a portion of the sensor array described herein), and the heat exchange between the finger and the individual sensing pixels in the underlying layer is monitored through temperature change measurement. Relatively high sensing pixel temperatures indicate low thermal conductivity, resulting in less heat loss between the sensing pixel and the finger and thus less heat exchange. Points with low thermal conductivity map localized valley structures of the fingerprint, while points with high thermal conductivity, i.e., high heat conduction / transfer, map localized ridge structures of the fingerprint. Points with intermediate thermal conductivity correspond to local transition regions between ridges and valleys. The temperature difference is measured using a sensing element (e.g., a fingerprint sensing pixel), and the measurement is processed to generate a fingerprint image of the fingerprint sensor.

[0054] Active thermal biometric sensors, such as fingerprint sensors, can be manufactured through large-area production processes, such as processes for forming low-temperature polysilicon (LTPS) thin-film transistors and devices. In this disclosure, the active thermal biometric sensor includes oxide semiconductor materials described herein. For example, in some embodiments, the oxide semiconductor material is used as the channel of a thin-film transistor in the biometric sensor. In some embodiments, the oxide semiconductor material is used in the thermistor or diode of the biometric sensor, for example, as a channel material.

[0055] As used herein, the term “microheater” is understood to encompass thin-film heaters, which can be two-terminal, such as thermistors or didos, or three-terminal, such as thin-film transistors. Microheaters are configured to convert electrical energy into thermal energy through Joule heating (also known as resistive heating or ohmic heating) as current flows through them. As used herein, the term “microtemperature sensor” is understood to include thin-film devices for measuring local temperature. When a thin-film heater has a temperature coefficient (in units of ΔV / °C), it also becomes a “microtemperature sensor,” and the voltage change (ΔV) associated with temperature can be used to detect temperature changes.

[0056] As used herein, the term "two-terminal" refers to a device such as a thermistor or diode. As used herein, the term "three-terminal" refers to a device such as a thin-film transistor.

[0057] When a biometric sensor, such as a fingerprint sensor, acquires a fingerprint pattern or image in "active thermal sensing" mode, the associated microheaters in the sensor array are turned on. When the sensor operates in "passive thermal sensing" mode, the associated microheaters are turned off.

[0058] "Capacitive sensing" refers to a type of sensing that uses measurement to detect changes in capacitance relative to a sensor element. In this disclosure, the sensor element may be made of a conductive material such as indium tin oxide (ITO), a thin metal film, a metal mesh, or any combination thereof. The change may be caused by human contact, such as a finger or hand. This is also called "capacitive touch."

[0059] The term "self-capacitance sensing" refers to a type of sensing that is performed, for example, by measuring the change in capacitance of one electrode acting as a capacitor with respect to the second electrode, which is ground.

[0060] The term "mutual capacitance sensing" refers to a type of sensing that is performed by measuring the change in capacitance between two electrodes.

[0061] The term "out-cell" means that the touch sensor and fingerprint sensor are formed on a separate sensor board independent of any display board. The resulting device may be called a "biometric sensor on display" device, such as a fingerprint on display (FoD) device.

[0062] The term "in-cell" means that the touch sensor and fingerprint sensor are placed within the display cell, and the display, touch sensor, and fingerprint sensor are all formed on the same substrate. The resulting device may be called an in-cell "biometric sensor on display" device, such as a fingerprint on display (FoD) device.

[0063] Capacitive touch sensing is classified into two categories: passive matrix and active matrix.

[0064] The term "active matrix" refers to a pixel matrix composed of independent pixels, each of which contains a transistor.

[0065] The term "passive matrix" refers to a pixel matrix with x and y coordinates where each pixel does not have its own dedicated transistor.

[0066] Passive matrix capacitors do not require thin-film transistors (TFTs) for operation. Active matrix capacitors require TFTs to drive the capacitors, and in this disclosure, the TFTs are preferably based on low-temperature polysilicon (LTPS) for temperature stability.

[0067] In this specification, the terms "large area" or "wide area" refer to the detection area in a biometric sensor, for example, in a fingerprint sensor, at least 20 mm × 20 mm (400 mm) 2 This refers to the region of ). In this specification, the terms "high resolution" or "high resolution" mean that the resolution of the biometric sensor is at least 500 pixels per inch (ppi).

[0068] "Impersonation" or "fingerprint impersonation" refers to the use of artificial or fake biometric patterns, such as fingerprints, to bypass biometric security systems and effectively impersonate the fingerprints of legitimate users in order to gain unauthorized access. "Impersonation prevention" or "fingerprint impersonation prevention," also known as fingerprint biometric detection, is a security measure that prevents unauthorized access to a system or device by detecting and rejecting attempts to use forged or duplicated fingerprints, thereby ensuring that only real, living fingers are used for authentication.

[0069] The anti-spoofing performance is characterized by the false rejection rate (FRR) and false recognition rate (FAR), which are recognized as industry-standard performance metrics for evaluating biometric authentication systems, including fingerprint sensors. These are used in industries such as consumer electronics, security, banking, and access control to evaluate the accuracy and reliability of biometric authentication. The false rejection rate (FRR) is defined as the percentage of times a fingerprint sensor incorrectly rejects a legitimate user's fingerprint and fails to authenticate. The FRR is calculated by dividing the number of false rejections by the total number of legitimate authentication attempts, and multiplying by 100 when expressed as a percentage. A high FRR leads to user frustration as authorized users are repeatedly denied access. A high FRR can be caused by poor sensor quality or low resolution, fingerprint contamination, damage, wear (e.g., cuts, scars, or moisture), incorrect finger placement or insufficient pressure, or environmental factors such as temperature or humidity.

[0070] False Identification Rate (FAR) refers to the percentage of times a fingerprint sensor incorrectly authenticates the fingerprint of an unauthorized user, granting access to someone who should not have it. FAR is calculated by dividing the number of false authentications by the total number of fraudulent authentication attempts, and multiplying by 100 when expressed as a percentage. A high FAR compromises security by increasing the risk of unauthorized access. This is extremely important in high-security applications such as banking or device unlocking. High FAR can result from the use of low-quality sensors with insufficient detailed information acquisition, vulnerabilities to (rare but possible) similar fingerprint patterns between users, or impersonation (e.g., fake fingerprints made of silicon or gelatin).

[0071] Therefore, high-quality biometric sensors are crucial to achieving the desired minimum FRR and FAR.

[0072] Organizations such as the International Organization for Standardization (ISO), the National Institute of Standards and Technology (NIST), and the FIDO Alliance have adopted biometric performance standards, such as FRR and FAR in ISO / IEC 19795 for biometric testing. FRR and FAR are often specified in the authentication process of biometric devices used in government-issued identity card systems or secure payment systems to ensure compliance with security and usability requirements.

[0073] Standards depend on the industry and application. For example, in consumer electronics such as smartphones, a good fingerprint sensor targets FRR < 1-2% and FAR 0.001-0.01% to balance user convenience and security. In high-security applications such as banks and government agencies, a low value such as FAR < 0.0001% (1 ppm) is desired, even if it means a slight increase in FRR.

[0074] This disclosure provides sensors or devices, apparatus, systems and methods for performing sensing such as biometric sensing. This disclosure also provides methods for manufacturing sensors or devices, apparatus and systems. For illustrative purposes only, this disclosure uses a finger as an exemplary object and a fingerprint as an example of a biometric pattern. The products and methods provided in this disclosure can generally be used to measure patterns on a partial thermally conductive surface of an object. For example, such an object may be the palm of a hand or the skin of another part of the human body. According to some embodiments, biometric sensing is combined with a display. The resulting device having a biometric sensor and a display is also called a “biometric sensor on display”. When the biometric sensor is a fingerprint sensor, the resulting device is called a “fingerprint on display” (FoD). Such FoD devices can be out-cell or in-cell.

[0075] This disclosure provides a large-area, high-resolution biometric sensor. The sensors and devices provided in this disclosure have excellent performance characteristics, such as anti-spoofing capabilities, characterized by extremely low FAR and FRR. For example, the FRR is less than 1% or less than 2%, e.g., less than 0.5% or less than 0.2%, and the FAR is between 0.001% and less than 0.01%, e.g., less than 0.001% or less than 1 ppm.

[0076] In Figures 1A to 10D, similar components are indicated by the same reference numerals, and for the sake of brevity, the descriptions of the structures described above with reference to the drawings will not be repeated. The methods described herein will be explained with reference to the exemplary structures shown in Figures 1A to 10D.

[0077] According to several embodiments, the Disclosure provides fingerprint-on-display (FoD) technology and methods for manufacturing the same, enabling the integration of large-area, high-resolution biometric sensors such as fingerprint sensors, touch sensors and fingerprint sensors based on capacitive and active thermal sensing technologies. The Disclosure also provides related devices, systems, methods for manufacturing the same and methods for using the same.

[0078] Fingerprint sensors are rapidly expanding their applications in smartphones, tablet computers, laptop computers, and other consumer electronics due to their significant advantages, such as being more convenient than PINs or passwords, offering higher biometric security than other identity verification methods, and being easier and less expensive to implement than facial recognition. As radio frequency identification (RFID) and near-field communication (NFC) are rapidly adopted in various smart card and smartphone payment platforms, and as smartphones are increasingly used in sensitive areas ranging from home security, personal healthcare, insurance, and banking to airline check-in and boarding procedures, there is an urgent need to enhance the security of smart cards, smartphones, and other consumer electronics to the next level without compromising user convenience.

[0079] One approach is to use larger-area fingerprint sensors, which would allow for the acquisition of more biometric information and improved identification accuracy. This can be achieved by shifting the manufacturing of fingerprint sensors from silicon wafer-based semiconductor fabs to thin-film transistor (TFT)-based display fabs. A key advantage of the latter approach is that, in addition to the more accurate, larger, and flexible standalone fingerprint sensors made possible by TFT fabs, TFT-based large-area fingerprint sensors can be easily integrated into various types of displays.

[0080] As described herein, TFT-based large-area fingerprint sensors can be integrated into various displays through either out-cell or in-cell configurations to realize fingerprint-on-display (FoD). The term "out-cell" means that the touch sensor and fingerprint sensor are formed on a separate sensor substrate independent of the display substrate. "In-cell" means that the touch sensor and fingerprint sensor are located within a display cell, and the display, touch sensor, and fingerprint sensor are all formed on the same substrate. The fingerprint sensor may be located on the same plane as the display cell or multiple cells.

[0081] Numerous attempts have been made to integrate various fingerprint sensor technologies, such as optical, capacitive, and ultrasonic, into displays. However, optical fingerprint sensors are extremely difficult to integrate into liquid crystal displays (LCDs) due to interference from the backlight unit. Furthermore, optical fingerprint sensors are inherently vulnerable to 2D image forgery (e.g., paper printouts). Capacitive fingerprint sensors are prone to malfunctions due to noisy electrical signals or sweaty fingers, and scaling up their size and resolution is extremely difficult. Ultrasonic fingerprint sensor technology appears to be compatible only with specific display types (flexible organic EL displays), significantly limiting its adoption in FoD.

[0082] A fingerprint sensor based on the principle of "active thermal sensing" comprises an array of pixels, each having a microheater and microtemperature sensor based on a thin-film device, and maps a fingerprint image based on minute temperature differences in the sensor surface area corresponding to the "valley" and "ridge" regions of the fingerprint. The microheater and microtemperature sensor within each pixel can be implemented by the same thin-film device, or the microheater and microtemperature sensor of each pixel can be implemented by two independent devices. When the sensor pixel is heated by the microheater, the local sensor surface area corresponding to the "valley" region of the fingerprint becomes hotter than the area corresponding to the "ridge" region. This is because heat dissipation in the "valley" region depends solely on thermal radiation, while in the "ridge" region, heat dissipation is possible by both thermal conduction and thermal radiation, and the latter is far more efficient. As a result of its operating principle, the active thermal fingerprint sensor can provide a larger and more stable signal that cannot be faked using 2D fingerprint images, and is therefore less susceptible to the problems caused by capacitive fingerprint sensors and ultrasonic fingerprint sensors.

[0083] On the other hand, a fingerprint sensor based on the principle of "passive thermal sensing" comprises an array of pixels, each having a micro-temperature sensor based solely on a thin-film device, and generates a fingerprint image based on minute temperature differences in the sensor surface area corresponding to the "valley" and "ridge" regions of the fingerprint.

[0084] Except in extremely hot ambient environments, such as the outdoors on a heatwave, the temperature of a living human finger is generally significantly higher than the surrounding environment in a comfortable indoor office environment due to the body's internal heat generation and the skin's insulating properties. The human body normally maintains a core temperature of approximately 37°C and keeps extremities like fingers as warm as possible through blood circulation. For example, even in a cold environment with an ambient temperature of approximately 0°C, a living human finger can maintain a temperature of approximately 10°C to 15°C.

[0085] When a living human finger touches a fingerprint sensor based on the principle of "passive thermal sensing," the local sensor surface area corresponding to the "ridge" region of the human fingerprint becomes hotter than the area corresponding to the "valley" region of the fingerprint because it is heated by both heat conduction and thermal radiation from the even hotter "ridge" region of the living human finger. On the other hand, heat transfer from the "valley" region of the human fingerprint to the corresponding sensor surface area occurs only by thermal radiation due to the presence of an air layer.

[0086] Therefore, the thermal pattern of a living human fingerprint, i.e., the temperature pattern of the "ridge" region relative to the "valley" region, is inverted in fingerprint images obtained using the "passive thermal sensing" principle and the "active thermal sensing" principle. In other words, under the most common conditions where the temperature of a living human finger is higher than the ambient environment and the temperature of the fingerprint sensor, fingerprint images scanned continuously using passive and active thermal sensing operations create thermal images in which the grayscale is inverted in the ridge and valley regions of the human fingerprint.

[0087] According to several embodiments, a fingerprint sensor having dual-mode (active thermal sensing and passive thermal sensing) operation can be provided to achieve robust anti-spoofing capabilities. Passive thermal sensing is not favorably used in existing sensors. However, the advantage of this dual-mode thermal measurement is that while passive thermal sensing evaluates skin temperature, active thermal sensing evaluates the heat capacity or thermal diffusivity of the skin. Measuring two different responses, the fingerprint images can be cross-verified to improve anti-spoofing performance. Furthermore, a fake or deceased person's fingerprint will normally remain at ambient temperature unless someone intentionally warms or cools it to mimic body temperature. The temperature of a living human finger is usually even more "regulated" and likely to be different from the ambient temperature.

[0088] Indium gallium zinc oxide (IGZO) thin-film transistors (TFTs) have been studied for the past 20 years as a low-cost alternative to low-temperature polysilicon (LTPS) TFTs for processing and driving high-resolution electronic displays, particularly displays with current-driven pixels such as OLED or micro-LED displays. The most mainstream IGZO TFTs used in existing displays are based on amorphous IGZO semiconductors. One of the main weaknesses of amorphous IGZO is its temperature instability. See, for example, M. Estrada, “Temperature dependence of the electrical characteristics up to 370 K of amorphous In-Ga-Zn-O thin film transistors”, Microelectronics Reliability, volume 56, January 2016, pp. 29-33. Because there are no grain boundaries, the channel carrier (electron) concentration increases rapidly with increasing temperature due to thermal activation, and these carriers can move freely without interference or restriction by grain boundaries. For this reason, amorphous IGZO TFTs tend to exhibit a more pronounced negative threshold voltage (Vth) shift in their transition characteristic curves compared to LTPS TFTs. The latter uses polysilicon as the channel semiconductor material, and the presence of grain boundaries that trap and inhibit carriers partially offsets the thermal activation enhancement of carriers at high temperatures, so the negative Vth shift in the LTPS TFT transition curve is not as pronounced.

[0089] To address the temperature instability issues of amorphous IGZO TFTs, crystalline IGZOs such as CAAC-IGZO (C-axis oriented crystalline indium gallium zinc oxide) have been developed in recent years, significantly improving the temperature stability of CAAC-IGZO-based TFTs. Other methods to improve the temperature stability of IGZO are also being studied, such as modifying the composition of IGZO to further strengthen the bond with oxygen in order to minimize oxygen loss at high temperatures and suppress the increase in carrier concentration associated with the formation of oxygen vacancies. It is known that adding cationic elements to IGZO or substituting existing cationic elements in IGZO with elements such as aluminum (Al), tin (Sn), titanium (Ti), tungsten (Ta), zirconium (Zr), cobalt (Co), nickel (Ni), hafnium (Hf), silicon (Si), fluorine (F), and germanium (Ge), as well as rare earth elements such as yttrium (Y) and radium (La), can help improve the temperature stability of TFTs. However, the chemical bond between the cation element and oxygen in IGZO or other oxide semiconductors is still an ionic bond, and not as strong as the covalent bond found between silicon atoms in polysilicon. Therefore, oxygen loss at high temperatures is unavoidable in IGZO or other types of oxide semiconductors, and the formation of oxygen vacancies makes it easy for the carrier concentration to increase sharply. For this reason, the negative shift of Vth with increasing temperature in most oxide semiconductors is more pronounced than in LTPS.

[0090] Oxide semiconductor TFTs with improved temperature stability generally exhibit decreased mobility, reduced carrier concentration, and increased sheet resistance. On the other hand, removing certain cation elements such as Ga from IGZO increases carrier concentration, reduces sheet resistance, and increases temperature instability; that is, the negative Vth shift becomes even more pronounced with increasing temperature.

[0091] The inherent temperature instability (or sensitivity) of oxide semiconductor-based TFTs poses a challenge for the display industry and also presents an opportunity to leverage the large negative Vth shift with temperature in temperature sensing applications of this disclosure. In this context, the negative Vth shift with temperature is defined as "temperature coefficient - K vt It is also known as "[...]." For example, a large negative Vth shift of -2.5V has been reported in amorphous IGZO TFTs between 300K (27℃) and 330K (57℃), resulting in a very good temperature coefficient: Kvt = -2.5V / 30℃ = -83mV / ℃. In active thermal fingerprint sensing applications, the characteristic of a significant negative Vth shift with temperature (large negative Kvt) makes oxide semiconductors an ideal candidate for active thermal sensing pixel elements. The very wide range of Kvt (reported from -9mV / ℃ to -83mV / ℃) reflects a very wide range of carrier concentrations and sheet resistances achievable in oxide semiconductor thin films, and oxide semiconductor thin films can be easily adjusted by adding or removing various cationic elements to IGZO as described above, in addition to various device processing knobs including processing temperature and atmosphere.

[0092] IGZO-based TFTs can be used as microheaters. See, for example, Katsumi Abe, “Simulation Study of Self-Heating and Edge Effects on Oxide-Semiconductor TFTs: Channel-Width Dependence,” IDW '2019, p. 461. In addition to being microheaters, IGZO-based TFTs can also be used simultaneously as microtemperature sensors. See Hoon Jeong, “Temperature Sensor Made of Amorphous Indium-Gallium-Zinc Oxide TFTs”, IEEE electron Device Letters, November 1, 2013. These properties make IGZO (and other oxide semiconductors with similar properties) ideally suited as “active thermal sensing” pixel elements as described herein. In particular, diode-connected IGZO TFTs are an ideal configuration because they behave similarly to two-terminal diodes and can simultaneously serve as both microheaters and microtemperature sensors when used as active thermal sensing pixel elements.

[0093] Other semiconducting oxide thin films can be used as excellent negative temperature coefficient (NTC) thermistors. Examples of these semiconducting oxides may include manganese, copper, silicon, cobalt, vanadium, nickel, and zinc metal oxides and mixed metal oxides thereof, and their room temperature sheet resistances ranging from 5 kΩ / sq to 500 kΩ / sq and temperature coefficients of resistance (TCR) ranging from -0.5% / K to -20% / K are also suitable candidates for thin-film devices that function as both microheaters and microtemperature sensors in the active thermal fingerprint sensors of this disclosure.

[0094] Currently, the FoD market is dominated by optical fingerprint sensor technology, ultrasonic fingerprint sensor technology, and the relatively minority capacitive fingerprint sensor technology. Optical technology involves placing the optical fingerprint sensor beneath the display (e.g., LCD or OLED display) or integrating it directly into the display as a so-called "in-cell" solution. In-cell types have the advantage of enabling fingerprint sensors with a larger area by utilizing thin-film transistor (TFT) array processes to manufacture the image sensor. Both active pixel sensors (PPS) and passive pixel sensors (APS) can be manufactured by integrating TFTs and photodiodes. However, challenges must be addressed in collecting these signals, as the light signals reflected from the ridges and valleys of the fingerprint tend to be scattered by the display structure, including glass.

[0095] Numerous attempts have been made to improve the collection of reflected light signals by manufacturing various types of micro-optical collimator structures such as microlenses, microtubes, or micropinholes. However, the design and manufacturing processes of the "in-cell" approach have proven to be extremely difficult, resulting in high costs.

[0096] In the "under-display" approach, the fingerprint sensor is placed beneath the display layer, such as the AMOLED display layer. In the "under-display" approach, optical or ultrasonic technology is used to acquire and recognize the user's fingerprint.

[0097] Under-display solutions are also extremely difficult. For example, in the case of OLED displays, it may be necessary to create an aperture in the OLED display glass to allow reflected light to reach the optical image sensor beneath the OLED glass, which is not feasible from a manufacturing standpoint and cannot support high-resolution fingerprint recognition. Under-display solutions for LCDs are even more difficult because it is impossible to create apertures in either the TFT glass or CF glass, making light collimation extremely difficult. Furthermore, all under-display optical sensors share the common drawback that most of the optical signal is lost due to light scattering by the display glass and shading by the display pixels. This problem is even more severe with small, expensive silicon-based optical image sensors (CCD or CMOS type) that are often used under displays.

[0098] Ultrasonic fingerprint sensor technology has a significantly limited range of applications in FoD due to limitations in ultrasonic transmission within display structures. Ultrasonic fingerprint sensors do not function in displays with an air layer, excluding their application to the vast majority of flat-panel displays based on rigid LCD or rigid AMOLED. Furthermore, ultrasonic fingerprint sensors only work with extremely limited screen protector materials that have a specific thickness to enable proper ultrasonic signal generation.

[0099] Conventional passive matrix capacitive touch sensors can detect either mutual capacitance signals or self-capacitance signals generated by finger contact. Mutual capacitance sensors have a capacitor at each intersection of rows (X) and columns (Y). When a finger touches near an intersection, a portion of the mutual capacitance between the row and column is coupled to the finger, reducing the capacitance at the intersection as measured by the system's electronics. Multiple touch points can be uniquely identified by the (X,Y) coordinates of all touch points. Self-capacitance sensors have a similar XY grid to mutual capacitance sensors, but the columns and rows operate independently, and the system's electronics measure the current from each electrode to ground. Each electrode forms one plate of the capacitor, with the other plate being ground or the user's finger. Since the human body is "added" to the system's capacitance, touch increases the measured self-capacitance.

[0100] However, despite the stronger signals from self-capacitance sensing, the electronic circuit can uniquely identify only a single touch point through capacitance changes detected independently for both the row and column intersecting a particular point. On the other hand, with two-point touch, capacitance changes are detected independently for two rows and two columns, but the system electronic circuit cannot distinguish which two-point set is being touched. Different combinations of two-point touches will produce the same capacitance change in the corresponding two rows and two columns.

[0101] Conventional passive-matrix mutual capacitive touch sensors are widely used in touch sensing solutions that require relatively coarse resolution (e.g., a few millimeters) for multi-touch functionality and low cost. Improving touch resolution is extremely difficult because, as touch resolution increases and touch element size decreases, parasitic and coupled capacitances increase rapidly, while the intended signal from the touch element simultaneously decreases rapidly.

[0102] On the other hand, active-matrix self-capacitive touch sensors offer the advantages of high-resolution touch, high-sensitivity touch signals, and low parasitic capacitance, as well as the convenience of combining capacitive touch and fingerprint authentication on the same glass substrate, making it possible to integrate them directly onto the top surface of any display glass.

[0103] One of the purposes of this disclosure is to provide novel and improved device structures, sensing configurations, and manufacturing methods for realizing a faster, more power-efficient, and more secure large-area high-resolution fingerprint sensor with embedded anti-spoofing characteristics. Another purpose of this disclosure is to integrate a touch sensor and a fingerprint sensor using a combination of capacitive sensing, active thermal fingerprint sensing technology, and passive thermal fingerprint sensing technology, so that the security and reliability of smartphones and other mobile / fixed electronic devices that require a higher level of security through the use of a large-area high-security fingerprint sensor, either as a standalone large-area fingerprint sensor or a full-screen FoD, can be improved.

[0104] When designing active thermal sensing pixels for fingerprint sensing or sensing of other fine features (e.g., palm print sensing), the two main configurations described herein can be employed.

[0105] Configuration 1 integrates a micro-temperature sensor and a micro-heater as a single thin-film device within each sensing pixel. In this scenario, the manufacturing of sensors with a sensing pixel array becomes even easier. If the thin-film device employed includes a diode or thin-film transistor based on IGZO or other oxide semiconductor channel material, the temperature coefficient (K) of such device is... vtThe temperature coefficient (TCR) of the thermistor semiconductor layer is preferably in the range of -2mV / °C to -200mV / °C, and more preferably in the range of -10mV / °C to -100mV / °C. Furthermore, the sheet resistance of the device semiconductor layer at room temperature is preferably in the range of kΩ / sq to 3MΩ / sq, and more preferably in the range of 20kΩ / sq to 500kΩ / sq. If the thin-film device used is a negative temperature coefficient (NTC) thermistor, its temperature coefficient of resistance (TCR) is preferably in the range of -0.5% / K to -20% / K, and more preferably in the range of -1% / K to -10% / K. Furthermore, the sheet resistance of the thermistor semiconductor layer at room temperature is preferably in the range of 5kΩ / sq to 3kΩ / sq, and more preferably in the range of 20kΩ / sq to 500kΩ / sq.

[0106] Configuration 2 of the active thermal sensing pixel involves manufacturing an independent micro-temperature sensor device and micro-heater device for each sensing pixel. In this scenario, an additional device manufacturing process is required, but it has the advantage of improving the sensor scanning speed when using a low-resistance conductive material such as metal as a common micro-heater line for all rows of sensing pixels, thereby enabling active heating on a row-by-row basis, unlike the pixel-by-pixel heating in Configuration 1.

[0107] The micro-temperature sensor device in this scenario can be a diode or thin-film transistor based on IGZO or other oxide semiconductor channel material. It is desirable that its temperature coefficient (Kvt) falls within the range of -2mV / °C to -200mV / °C, and that the sheet resistance of the device semiconductor layer at room temperature falls within the upper end of the known range of interest, for example, from 200kΩ / sq to 10GΩ / sq.

[0108] In this scenario, the micro-temperature sensor device can also be a negative temperature coefficient (NTC) thermistor, and it is desirable that its temperature coefficient of resistance (TCR) falls within the range of -2% / K to -20% / K. It is also desirable that the sheet resistance of the thermistor semiconductor layer at room temperature falls within the upper limit of the known range of interest, for example, between 200 kΩ / sq and 3 MΩ / sq.

[0109] To eliminate or minimize the self-heating effect associated with the micro-temperature sensor in Configuration 2, a higher sheet resistance is preferable. This allows Configuration 2, an active thermal sensing pixel, to function as a passive thermal sensing pixel when the column-shared micro-heater line is off during sensor operation. This is because the amount of heat generated is extremely small when the micro-temperature sensor is operating to measure the temperature difference between the ridge and valley regions of the fingerprint. Images scanned continuously using passive and active thermal sensing operations create a thermal image with inverted grayscale in the ridge and valley regions of the fingerprint, at least in the most common scenario where the human body temperature is higher than the ambient temperature. This remarkable feature enables the highly desirable anti-forgery capability of the fingerprint sensor constructed in Configuration 2.

[0110] According to several embodiments, the Disclosure provides a large-area biometric sensor (such as a fingerprint sensor) that integrates capacitive touch sensing and active thermal fingerprint sensing on a single monolithic sheet on a glass or flexible substrate, wherein the sensing pixels in the active thermal fingerprint sensing region comprise a two-terminal device such as a diode, a diode-connected TFT or thermistor, or a three-terminal device such as a thin-film transistor based on an oxide semiconductor. In some embodiments, an oxide semiconductor is used as the channel material for the TFT (or diode or thermistor). Suitable examples of oxide semiconductors include, but are not limited to, amorphous or crystalline indium gallium zinc oxide (IGZO) or modified IGZO. The temperature stability of TFTs can be improved by incorporating additional cationic elements into IGZO or by substituting existing cationic elements in IGZO with elements such as aluminum (Al), tin (Sn), titanium (Ti), tungsten (Ta), zirconium (Zr), cobalt (Co), nickel (Ni), hafnium (Hf), silicon (Si), fluorine (F), and germanium (Ge), as well as rare earth elements such as yttrium (Y) and radium (La). (The greater the degree of instability, the better.) A moderate level of TFT temperature stability is achieved to balance the need for active temperature sensing and environmental stability. Utilizing the relatively low stability of oxide semiconductor materials for active temperature sensing is a unique approach in this disclosure and yields remarkably good results in the biometric devices described in the specification.

[0111] In this specification, the substrates used in TFT manufacturing include, but are not limited to, glass and glass-supported polyimide substrates. The manufacturing processes and apparatus described herein eliminate the need to use or contact silicon wafer-based TFTs because silicon wafer bases are extremely small and very expensive.

[0112] In this disclosure, active thermal biometric sensors include oxide semiconductor materials described herein. For example, in some embodiments, oxide semiconductor materials are used as channels in thin-film transistors within biometric sensors. In some embodiments, oxide semiconductor materials are used in thermistors or diodes of biometric sensors, for example, as channel materials. The (considered unstable) temperature sensitivity of oxide semiconductors such as IGZO and modified IGZO yields surprisingly good results in this disclosure. This is because TFTs, diodes, or thermistors containing oxide semiconductors can be used as both micro-temperature sensors and micro-heaters, particularly in active thermal sensing.

[0113] Furthermore, the optical transparency of oxide semiconductors is also utilized, particularly in both sensing and display applications. Oxide semiconductors may have transmittances in the range of 50% to 99.9% of visible light, for example, in the range of 50% to 98%, 60% to 98%, 70% to 98%, 80% to 99%, 80% to 98%, 80% to 95%, or other suitable ranges. Apparatus such as the FoD apparatus provided in this disclosure may have an aperture ratio greater than 50%, for example, an aperture ratio greater than 60%, greater than 70%, greater than 80%, or greater than 90%. The aperture ratio refers to the ratio of the area of ​​the light-sensing region of a pixel to its total area. A higher aperture ratio means that more light is emitted in a given display area.

[0114] Oxide semiconductors may be amorphous, or they may have a crystalline or polycrystalline structure.

[0115] In this disclosure, the TFT containing an oxide semiconductor is an active thermal sensing device. The transistors driving the sensor matrix or in the peripheral circuitry need to be thermally stable and less susceptible to temperature changes, and in some embodiments, unless otherwise specified, they are preferably low-temperature polysilicon (LTPS) based.

[0116] In either or both of the configurations 1 and 2 described herein, the sensor containing the oxide semiconductor and the resulting device may be operated.

[0117] In configuration 1, the two-terminal or three-terminal device functions as both a microheater and a microtemperature sensor in each detection pixel.

[0118] In configuration 2, the two-terminal or three-terminal device functions solely as a micro-temperature sensor at each pixel, and a separate (e.g., metal-based) microheater, manufactured independently, is shared across the entire row of sensing pixels.

[0119] In configuration 2, fingerprint images are acquired in both "active thermal sensing" mode (with the microheater on) and "passive thermal sensing" mode (with the microheater off), and the fingerprint images acquired in these two different modes are compared and contrast-analyzed to enhance the fingerprint sensor's anti-spoofing performance.

[0120] This disclosure further discloses oxide semiconductor-based two-terminal or three-terminal devices, such as diodes, thin-film transistors, diode-connected thin-film transistors, thermistors, etc., that simultaneously function as a microheater and a microtemperature sensor for each pixel of an active thermal fingerprint sensor. Optionally, additional microheaters can be formed from a transparent conductive oxide (TCO) such as ITO or ZnO:Al, which is applied to a single fingerprint sensor or FoD.

[0121] Non-oxide materials such as silicon carbide, tin selenide, tantalum nitride, or polysilicon can be used to form thermistors or diodes that simultaneously function as microheaters and microtemperature sensors. Optionally, additional microheaters can be formed from Ag, Al, Au, CNT, Cr, CrN, Cu, ITO, ZnO:Al, Ni, NiCr, Pt, Si nanowires, SiC, Sn, SnO2, Ta2O5, Ti, W, and various combinations thereof, which are applied to a single active thermal fingerprint sensor.

[0122] The top surface of the sensor can be protected by a transparent or opaque hard coat, and the large-area fingerprint sensor can optionally use a capacitive or thermal scanning method, which allows for configuration of size and resolution.

[0123] This disclosure provides a low-cost, high-speed combination of a coarse-grid passive-matrix inter-capacitive touch sensor with a dense-grid active-thermal fingerprint sensor and a transparent hard coat for integration on the top surface of any type of display panel, in order to enable multi-touch detection using a coarse-capacitive grid and fingerprint sensing using a dense active-thermal grid in the same display device.

[0124] This disclosure provides a combination of a dense grid active self-capacitive touch and fingerprint sensor with a dense grid active thermal fingerprint sensor in order to increase the fake finger rejection rate and ensure high security of the fingerprint sensor. The fake finger material needs to have a predetermined set of electrical, mechanical, and surface energy properties that are sufficiently close to those of a human finger in order to deceive a capacitive fingerprint sensor, but to deceive an active thermal fingerprint sensor it needs to have a different set of electrical, mechanical, and surface energy properties in addition to extremely unique thermal properties. Therefore, the possibility of the fake finger material deceiving both a capacitive fingerprint sensor and an active thermal fingerprint sensor is greatly reduced.

[0125] This disclosure also provides combining an active matrix-driven self-capacitive touch sensor with a transparent hard coat to enable multi-touch detection using coarse grid self-capacitive scanning and fingerprint sensing using dense grid active thermal scanning on the same display device. Transparent oxide semiconductors such as IGZO can be used as channel materials for in-pixel switching TFTs, and transparent conductive oxides (TCOs) such as ITO can be used as electrodes for self-capacitive sensing pixel elements. LTPS TFTs or oxide semiconductor (e.g., IGZO)-based TFT peripheral circuits for coarse grid touch sensing and dense grid fingerprint sensing can be fabricated on a sensor substrate to minimize the number of external connections to an application-specific integrated circuit (ASIC).

[0126] This disclosure provides in-cell fingerprint and touch sensors integrated into the TFT backplane of active-matrix light-emitting displays such as AMOLEDs, microLED displays, and electroluminescent quantum dot displays such as quantum dot light-emitting diodes (QD-LEDs). The touch sensor can be based on either a passive-matrix mutual capacitance scheme or an active-matrix self-capacitance scheme. The fingerprint sensor can be based on an active thermal principle and optionally combined with passive thermal sensing. TFTs based on transparent oxide semiconductors or opaque LTPS can be used to drive display pixels or self-capacitance pixels, and transparent conductive oxides (TCOs) such as ITO or opaque metals can be used as capacitive touch electrodes.

[0127] This disclosure provides capacitive and thermal scanning touch and fingerprint sensor on-display systems in which the size (or area) and resolution are configurable to save scanning time and power consumption.

[0128] Different embodiments of the biometric authentication sensor 100 described herein are shown in Figures 1A to 10D and described below. In each sensor or device, a plurality of pixels are provided with thermal sensing pixels configured to operate on at least the active thermal sensing principle, and a low-power thermal pulse is applied to the thermal sensing pixels and a response corresponding to the biometric authentication pattern is measured.

[0129] In some embodiments, each pixel array comprises multiple pixels arranged in multiple rows and multiple columns. Each pixel array includes thermal sensing pixels configured to operate on at least an active thermal sensing principle, wherein a low-power thermal pulse is applied to each pixel array and a response corresponding to a biometric pattern is measured. For thermal sensing, each pixel in the pixel array may include one or more diodes connected in series between the pixel rows and pixel columns.

[0130] In this disclosure, the pixel based on active thermal sensing includes the oxide semiconductor material described herein.

[0131] According to some embodiments, each pixel array comprises a capacitance sensing grid having capacitance sensing nodes distributed to each pixel array. The capacitance sensing grid is configured to detect the presence and / or rolling motion and position of an object. The capacitance sensing nodes may be mutual capacitance sensing nodes or self-capacitance sensing nodes. Self-capacitance sensing nodes are configured to be a passive matrix or an active matrix addressed by an array of thin-film transistors. Mutual capacitance sensing nodes are configured to be an addressed passive matrix.

[0132] Figures 1A and 1B show an example (Configuration 1) of a fingerprint sensor array 102 in which a micro temperature sensor and a micro heater are incorporated into each pixel according to several embodiments. The fingerprint sensor array 102 is an example of a biometric authentication sensor 100.

[0133] Referring to Figures 1A-1B, the sensor layer 40 (also called the sensing layer) is placed on the substrate 30 (also called the sensor substrate). Examples of the substrate 30 include, but are not limited to, glass and polyimide-coated glass. The substrate may also be a flexible substrate.

[0134] The sensor layer 40 comprises a pixel matrix having multiple pixels, which are configured to measure biological patterns, including, for example, the ridges and valleys of finger 2. The sensor layer 40 includes a micro-temperature sensor, a micro-heater, or a combination thereof within each pixel. In the configuration shown in Figures 1A to 1B, the sensor layer 40 includes a combination 41 of a micro-temperature sensor and a micro-heater within each pixel.

[0135] Examples of micro-temperature sensors, micro-heaters, or combinations thereof are selected from two-terminal devices such as thermistors and diodes or three-terminal devices such as thin-film transistors (TFTs). Micro-temperature sensors, micro-heaters, or combinations thereof include oxide semiconductor materials described herein. For example, oxide semiconductor materials are used as channels in TFTs. Oxide semiconductor materials can also be used in the manufacture of thermistors or diodes. Oxide semiconductor materials such as IGZO or modified IGZO can be used as channel materials. TFTs, diodes, thermistors, or combinations thereof can be used as temperature sensor and micro-heater combinations 41. When IGZO or modified IGZO is used as a semiconductor material, diode-connected TFTs are preferred.

[0136] In some embodiments, the microheater can be made of a conductive material other than an oxide semiconductor material, such as a metal. Metals and other highly conductive materials can be used only as microheaters; they are not typically good temperature sensors and therefore can only be used when the microheater and temperature sensor are separate, and they cannot be combined.

[0137] In this configuration shown in Figures 1A-1B, the manufacturing of a sensor having an array of sensing pixels becomes even easier. If the thin-film device employed includes a diode or thin-film transistor based on IGZO or other types of oxide semiconductor channel materials, the temperature coefficient (K) of such device is... vt It is desirable that the temperature coefficient of resistance (TCR) of the thermistor semiconductor layer be in the range of -2 mV / °C to -200 mV / °C, and more preferably in the range of -10 mV / °C to -100 mV / °C. Furthermore, it is desirable that the sheet resistance of the semiconductor layer of the apparatus at room temperature be in the range of 5 kΩ / sq to 10 gΩ / sq, and more preferably in the range of 50 kΩ / sq to 1 gΩ / sq. If the thin-film apparatus used is a negative temperature coefficient (NTC) thermistor, it is desirable that its temperature coefficient of resistance (TCR) be in the range of -0.5% / K to -20% / K, and more preferably in the range of -1% / K to -10% / K. Furthermore, it is desirable that the sheet resistance of the thermistor semiconductor layer at room temperature be in the range of 5 kΩ / sq to 3 mΩ / sq, and more preferably in the range of 20 kΩ / sq to 500 kΩ / sq.

[0138] Figures 2A-2B show an example (Configuration 2) of a fingerprint sensor array 104 having individual micro-temperature sensors and micro-heater lines according to several embodiments. The fingerprint sensor array 104 is an example of a biometric authentication sensor 100.

[0139] Referring to Figures 2A-2B, the sensor layer 40 is located on the substrate 30. The sensor layer 40 comprises a pixel matrix having a plurality of pixels configured to measure, for example, the biological pattern of a finger 2. In the sensor layer 40, the micro-temperature sensor and the micro-heater are separated from each other. For example, as shown in Figures 2A-2B, the sensor layer comprises micro-heater lines 42 and pixels equipped with micro-temperature sensors 44. Each micro-heater line 42 is located below a row of pixels equipped with micro-temperature sensors 44. The micro-heater lines 42 may be formed of metal or other conductive material. The micro-temperature sensor 44 is a TFT, diode, thermistor, or any combination thereof, and includes oxide semiconductor material.

[0140] In this configuration, as shown in Figures 2A-2B, an additional device manufacturing process is required. However, when a low-resistance conductive material such as metal is used as a microheater line common to all rows of sensing pixels, there is an advantage in that the sensor scan speed is improved. This allows for sequential active heating on a row-by-row basis, unlike the pixel-by-pixel heating in Configuration 1. The micro-temperature sensor device in this configuration can be a diode or thin-film transistor based on IGZO or other oxide semiconductor channel materials. Its temperature coefficient (K vt It is desirable that the voltage falls within the range of -2mV / °C to -200mV / °C, and that the sheet resistance of the semiconductor layer of the device at room temperature falls within the upper limit of the known range of interest, for example, from 200kΩ / sq to 10GΩ / sq.

[0141] The micro-temperature sensor device of Configuration 2 shown in Figures 2A-2B can be a negative temperature coefficient (NTC) thermistor. It is desirable that its temperature coefficient of resistance (TCR) falls within the range of -2% / K to -20% / K, and that the sheet resistance of the thermistor semiconductor layer at room temperature falls within the upper limit of the known range of interest, for example, between 200 kΩ / sq and 3 MΩ / sq. Even higher sheet resistance is preferable to eliminate or minimize the self-heating effect associated with the micro-temperature sensor of Configuration 2. This allows the active thermal sensing pixel of Configuration 2 to function as a passive thermal sensing pixel when the column-shared microheater line is off during sensor operation. This is because very little heat is generated when the micro-temperature sensor operates to measure the temperature difference between the ridge and valley regions of a fingerprint.

[0142] Under the most common scenario where the temperature of a living human finger is higher than the ambient temperature and the temperature of the fingerprint sensor, continuously scanned fingerprint images using passive and active thermal sensing operations create grayscale thermal images inverted in the ridge and valley regions of the fingerprint, and this remarkable feature enables the highly desirable anti-forgery capability of the fingerprint sensor constructed in configuration 2.

[0143] During passive thermal sensing operation, the likelihood of a forged fingerprint or a dead person's finger maintaining the same temperature distribution (or temperature map) along the ridges and valleys of a living human fingerprint is extremely low. Attempts to match the body temperature of a living human by warming the forged or dead person's finger (when the ambient temperature is lower than body temperature) or by cooling the forged or dead person's finger (when the ambient temperature is higher than body temperature) will result in a difference in thermal conductivity between the skin of a living human finger and the skin of a forged or dead person's finger. This means that the heat transfer rate of a living human finger and the resulting dynamic temperature distribution (or temperature map) will be very different from that of a forged or dead person's finger. Due to this difference, forged or dead people's fingers can be easily filtered out by multiple scans at pre-set time intervals using passive thermal scanning alone, active thermal scanning alone, or a combination of passive and active thermal scanning, and by active thermal scanning at pre-set times.

[0144] Figure 3 shows an exemplary apparatus 202 having an out-cell type fingerprint sensor on display (FoD) structure based on capacitive touch and active thermal fingerprint sensors according to several embodiments. Exemplary apparatus 202 is an example of apparatus 200.

[0145] Referring to Figure 3, an exemplary device 202 comprises a display layer 10 configured to display information, a thin adhesive layer 20 placed on the display layer 10, a sensor substrate 30 placed on the adhesive layer 20, and a sensor layer 40 placed on the sensor substrate 30. The adhesive layer is made of an optically transparent adhesive (OCA) having an acceptable level of transparency so that the displayed information is visible from the top surface of the device. A transparent hard coat 50 may be placed on the sensor layer 40.

[0146] In some embodiments, each of the sensors shown in Figures 1A-1B and 2A-2B further comprises a capacitive touch sensing element as described herein. The capacitive touch sensing element is self-capacitive or mutually capacitive and is active-matrix or passive-matrix. For example, in some embodiments, the capacitive touch sensing element is a passive-matrix mutually capacitive touch sensor or an active-matrix self-capacitive touch sensor.

[0147] The sensor has excellent anti-spoofing performance. For example, as described herein, in some embodiments, the capacitive touch sensing element is an active self-capacitive touch sensor used in combination with active thermal sensing to improve anti-spoofing performance. As another example, as described herein, the thermal sensing pixel comprises a passive thermal sensing pixel used in combination with active thermal sensing to improve anti-spoofing performance.

[0148] The sensors shown in Figures 1A-1B and 2A-2B are applicable to the active thermal layer of the FOD apparatus shown in Figures 3-8B. Figures 1A-1B and 2A-2B show standalone biometric devices, such as fingerprint sensors, in several embodiments, while Figures 3-8B show FOD apparatuses in several embodiments. The sensors shown in Figures 1A-1B and 2A-2B can be used in the active thermal layer of the FOD device. Therefore, various combinations of the sensors in Figures 1A-1B and 2A-2B and the apparatuses in Figures 3-8B are possible. In each apparatus, the biometric sensor can be operated based on the active thermal principle, and optionally, it can be operated in combination with the passive thermal principle to improve anti-spoofing performance. The transparency of oxide semiconductor materials such as IGZO or modified IGZO used in these fingerprint sensors makes them ideally suited for out-cell FoD applications because the oxide semiconductor material does not block light emitted from the display.

[0149] Figure 3 shows an embodiment of the apparatus 200 having the FoD structure provided in this disclosure.

[0150] In Figure 3, the sensor structure having a sensor substrate 30 and a sensor layer 40 is placed on a display layer 10. An adhesive layer 20 can be placed between the sensor substrate 30 and the display layer 10. A transparent hard coat 50 is placed on the sensor layer 40. The display layer 10 is configured for display and may have any suitable structure, including, for example, a liquid crystal display (LCD), an active matrix light-emitting diode (AMOLED), an electronic paper display (EPD), or other suitable display device. The adhesive layer 20 contains an optically transparent adhesive suitable for display applications. It may also contain a curable polymer that is cured in the device. As shown in Figure 3, the sensor layer 40 has a pixel matrix 47 having active thermal sensing pixels 46 and capacitive touch and finger sensing pixels 48. The pixel matrix is ​​shown as a black block in Figure 3 and in more detail in Figures 4A-4B. Further details are shown in Figures 7A-7B in relation to in-cell FoD.

[0151] In the sensor layer 40, a transparent oxide semiconductor-based microheater and sensor array can be used for low-power active pixels. Transparent conductive oxides (TCOs) such as ITO can be used for mutual capacitance or self-capacitance sensing electrodes. Transparent oxide semiconductor-based TFTs (IGZO, etc.) can be used for switching the active matrix self-capacitance pixel electrodes.

[0152] The FoD structure shown in Figure 3 combines capacitive touch sensing and active thermal fingerprint sensing. This exemplary device includes full-screen capacitive touch and active thermal fingerprint sensing with TFT peripheral circuitry for driving and signal reading. Two types of scenarios exist for the exemplary device shown in Figure 3: Scenario 1: Coarse grid passive matrix mutual capacitive touch and dense active thermal fingerprint sensing, and Scenario 2: Dense active thermal fingerprint sensing added to dense active matrix self-capacitive touch and fingerprint sensing to enhance false finger rejection capability.

[0153] In Scenario 1, full-screen passive-matrix mutual capacitive touch sensing is employed to achieve reliable and low-cost multi-touch position sensing functionality, while full-screen active thermal fingerprint sensing is employed to ensure the acquisition of high-quality fingerprint images. Low-temperature polysilicon (LTPS) TFTs or oxide semiconductor (e.g., IGZO) TFT peripheral circuits are used to drive and read signals from both the coarse mutual capacitive touch sensor and the dense active thermal fingerprint sensor, minimizing the number of external connections to the application-specific integrated circuit (ASIC).

[0154] In Scenario 2, dense grid active self-capacitive touch and fingerprint sensing is combined with dense grid active thermal fingerprint sensing to improve the ability to reject fake fingers. This is because it is extremely difficult to find a fake finger material that satisfies the requirements of both capacitive sensing and thermal sensing in both dry and wet conditions, such as human finger skin. The active matrix-addressed self-capacitive sensor consists of self-capacitive electrodes for each matrix pixel in the sensing region, which can be independently switched on or off by intrapixel thin-film transistors (TFTs). This provides the advantages of high touch sensing resolution, large touch signals, and low parasitic capacitance, as well as the convenience of combining full-screen capacitive touch position detection and fingerprint sensing using the same array of sensing pixels.

[0155] To ensure good visibility of the displayed content, an active thermal fingerprint sensing array is constructed using transparent oxide semiconductor-based thin-film microheaters and micro-temperature sensors. Oxide semiconductors with appropriate composition and surface resistance are known to simultaneously provide excellent microheaters and micro-temperature sensors, facilitating the manufacture of two-terminal devices (e.g., diodes or thermistors) or three-terminal devices (e.g., thin-film transistors) that function simultaneously as heaters and temperature sensors, thereby providing low-power active thermal fingerprint sensing pixels.

[0156] Examples of such thin-film oxide semiconductors for two-terminal devices include zinc oxide, titanium oxide, titanium zinc oxide, or zinc titanium oxide (doped or undoped with transition metals such as cobalt or nickel). Other semiconductor oxide thin films known as excellent negative temperature coefficient (NTC) thermistors, such as metal oxides and mixed metal oxides of manganese, copper, silicon, cobalt, vanadium, nickel, or zinc, with surface resistances ranging from 5 kΩ / sq to 500 kΩ / sq at room temperature and temperature coefficient of resistance (TCR) ranging from -0.5% / K to -20% / K, are suitable candidates for thin-film devices that function as both microheaters and microtemperature sensors for active thermal fingerprint sensors. Transparent conductive oxides (TCOs) such as ITO can be used as the upper and lower electrodes of mutually capacitive touch sensing elements in Scenario 1, and as single electrodes for self-capacitive touch sensing pixel elements and fingerprint sensing pixel elements in Scenario 2. To ensure good signals for capacitive and thermal sensing, a transparent hard coat is applied to the upper surface of the touch sensor and fingerprint sensor in Scenario 1 or Scenario 2, which significantly improves the signal-to-noise ratio (SNR) and fingerprint image quality compared to other conventional techniques that use cover glass for protection. Examples of suitable transparent hard coatings include, but are not limited to, nitride-based SiNx, BN, AlN, and any combination thereof.

[0157] Figure 4A shows an example (Scenario 1) of the exemplary device shown in Figure 3, which has coarse grid passive matrix mutual capacitive touch sensing and a dense active thermal fingerprint sensor according to several embodiments. Figure 4A shows a plan view of Scenario 1 of Figure 3, which shows the combination of coarse grid passive matrix mutual capacitive touch sensing and dense active thermal fingerprint sensing. Coarse grid capacitive touch allows for rapid detection of the finger touch position, and for this reason, a high-resolution scan by the active thermal fingerprint sensor is triggered only in the area where the finger is in contact, saving the total scan time and power consumption required for fingerprint sensing across the entire screen.

[0158] Figure 4B shows another example (Scenario 2) of the exemplary apparatus of Figure 3 having a dense grid active matrix self-capacitive touch and fingerprint sensor and a dense grid active matrix fingerprint sensor according to several embodiments. Figure 4B shows a plan view of Scenario 2 of Figure 3 showing a combination of a dense grid active self-capacitive touch and fingerprint sensor and a dense grid active thermal fingerprint sensor. Active matrix self-capacitive elements are physically configured to form a dense grid, but the dense grid active matrix self-capacitive pixels can be scanned row by row, in which case both position touch sensing and fingerprint sensing functions can be realized simultaneously. Alternatively, the self-capacitive pixels can be sparsely scanned (i.e., rows can be skipped) to function only as coarse-scan touch sensing pixels. The exemplary apparatus having the configuration of Figure 4B has a higher resolution than that of Figure 4A.

[0159] A transparent hard coat 50, such as a nitride-based thin film coating, may be used to significantly improve SNR and fingerprint image quality by ensuring significantly superior signal (capacitive and thermal) compared to other competing technologies.

[0160] In some embodiments, the sensor layer may have a pixel matrix that is a separate segment logically divided within the pixel matrix and is individually controllable. Exemplary devices 200, such as 202, 204, 206, and 208, which have an FOD structure, further include other components such as a plurality of application-specific integrated circuits (ASICs) connected to the sensor layer 40. Each ASIC is connected to the sensor layer 40 via a sensorflex printed circuit board (PCB) and conductive pads. Each ASIC is configured to acquire image data of a target biometric pattern measured by at least one pixel array. Each pixel array is configured to be driven and scanned independently by one or more of the plurality of ASICs.

[0161] The apparatus 200 may further include one or more display diver integrated circuits (ICs) and display flexible printed circuit boards (FPCs) connected to the display layer 10.

[0162] A microcontroller unit (MCU) may be coupled with multiple ASICs and display driver ICs. The MCU comprises one or more processors and at least one tangible, non-temporary, machine-readable medium on which one or more programs configured to process image data, display information and / or the operation of the device 200 or a system including the device 200 are encoded.

[0163] The sensor may further comprise a plurality of support circuits. Each pixel array is connected to at least one support circuit. In some embodiments, the sensor in the system may further comprise a plurality of switches. Each switch is connected to one or more support circuits and one or more ASICs. Each pixel array is configured to be driven and scanned independently by one or more of the plurality of ASICs via one or more switches.

[0164] Figure 5 shows another embodiment of exemplary apparatus 204 having an out-cell FoD structure based on an active-matrix self-capacitive touch sensor and an active thermal fingerprint sensor according to several embodiments. Exemplary apparatus 204 is an example of apparatus 200. The FoD structure is based on an active-matrix address self-capacitive element for touch sensing and an active thermal element for fingerprint sensing. To minimize the number of external connections to the application-specific integrated circuit (ASIC), LTPS TFT or oxide semiconductor (e.g., IGZO) based TFT peripheral circuits for coarse grid touch sensing and dense fingerprint sensing can be formed on the sensor substrate.

[0165] To ensure good visibility of the displayed content, transparent oxide semiconductors (e.g., IGZO) can be used as channel materials for TFTs for in-pixel switching, and transparent conductive oxides (TCOs) such as ITO can be used as electrodes for self-capacitive sensing pixel elements. To improve the signal quality of capacitive sensing, transparent hard coats (e.g., nitride-based SiNx, BN, AlN, etc.) can be formed on the upper surfaces of touch sensors and fingerprint sensors. As a result, the signal-to-noise ratio (SNR) and fingerprint image quality are significantly improved compared to conventional technologies that employ protective cover glass.

[0166] Referring to Figure 5, a full-screen active-matrix self-capacitive touch sensor and an active-matrix fingerprint sensor are positioned on top of any display. The sensor structure, having a sensor substrate 30 and a sensor layer 40, is positioned on top of the display structure layer 10. An adhesive layer 20 can be positioned between the sensor substrate 30 and the display layer 10. A transparent hard coat 50 is positioned on top of the sensor layer 40.

[0167] The TFT peripheral circuit is used for coarse touch sensing and dense fingerprint sensing. In the sensor layer 40, transparent oxide semiconductor-based in-pixel TFTs (IGZO, etc.) and transparent self-capacitive electrodes (ITO, etc.) can be used.

[0168] Transparent hard coatings, such as nitride-based thin film coatings, are used to ensure significantly superior signal, signal-to-noise ratio (SNR), and fingerprint image quality compared to other competing technologies.

[0169] Figure 6 shows an example of the exemplary device shown in Figure 5, which has a configuration combining coarse grid active matrix self-capacitive touch sensing pixels and dense grid active thermal fingerprint sensing pixels (top view in Figure 5) according to several embodiments.

[0170] Figures 7A-7B show exemplary apparatus 206 having an in-cell side-by-side top-emitting OLED or microLED with coarse-grid mutual-capacitive touch sensors and dense-grid active thermal fingerprint sensors according to several embodiments. Exemplary apparatus 206 is an example of apparatus 200. Figure 7B is a plan (top) view showing a sub-row of the sensor array in the exemplary apparatus of Figure 7A, showing the density of light-emitting pixels, mutual-capacitive touch pixels and active thermal sensing pixels according to several embodiments. In Figure 7B, the letters “G”, “R”, and “B” represent the green, red, and blue sub-pixels for display, respectively.

[0171] An exemplary apparatus 206 comprises a substrate 30, an active layer 60 disposed on the substrate 30, and a transparent hard coat 50 disposed on the active layer 60. The substrate 30 is for both sensing and display and may be called a "sensor and display substrate." The active layer 60 comprises pixels for sensing and display, integrating both the sensor layer and the display layer into a single layer. In some embodiments, the active layer 60 may include a thin film encapsulant 62.

[0172] Figures 7A-7B show other embodiments of the FoD structure of this disclosure in which a coarse-grid passive-matrix mutual-capacitance touch sensor and a dense-grid active thermal fingerprint sensor are integrated into the display structure itself by a so-called in-cell FoD approach. Display pixels 12, such as side-by-side top-emitting OLED or micro-LED pixels, are integrated with mutual-capacitance touch sensing pixels 48 and active thermal fingerprint sensing pixels 46 on the same glass sheet. The exemplary apparatus 206 also includes a TFT 11 for the display pixels, and the mutual-capacitance touch sensing pixels 48 have an upper electrode 48a and a lower electrode 48b. The upper and lower electrodes shown in Figure 7B are separated from each other as shown in Figure 7A. To minimize connections to external ASICs, TFT-based peripheral circuits can be employed for addressing the OLED or micro-LED emitting pixels, mutual-capacitance touch sensing pixels and active thermal fingerprint sensing pixels. The TFTs within each pixel (at least two TFTs for each light-emitting subpixel) and the TFTs for peripheral circuits can be based on either transparent oxide semiconductors (such as IGZO) or opaque LTPS TFTs. The TFTs 11 for the display pixels are of a different type from the TFTs for active thermal sensing for biometric authentication. The TFTs 11 for the display pixels are preferably made of LTPS-type TFTs for stability under various temperatures. The TFTs for active thermal sensing are preferably made of oxide semiconductor materials such as IGZO or modified IGZO for temperature sensitivity in temperature sensing.

[0173] Referring to Figures 7A-7B, TFTs based on transparent oxide semiconductors or opaque LTPS can be used as display pixels. Transparent conductive oxides (TCOs), such as ITO, or opaque metals can be used as mutual capacitance touch electrodes.

[0174] Figures 8A and 8B show an exemplary device 208 having a dense grid active matrix self-capacitive touch sensor and an active thermal fingerprint sensor with in-cell side-by-side top-emitting organic light-emitting diodes (OLEDs) or micro-LEDs. Figure 8A is a cross-sectional view showing the sensor array. Figure 8B is a top view showing a partial row of the sensor array. This exemplary device 208 is an example of device 200.

[0175] Similar to exemplary apparatus 206, exemplary apparatus 208 comprises a substrate 30, an active layer 60 disposed on the substrate 30, and a transparent hard coat 50 disposed on the active layer 60. The active layer 60 comprises pixels for sensing and display, integrating both the sensor layer and the display layer into a single layer. In some embodiments, the active layer 60 may have a thin film encapsulant 62. The active layer 60 comprises display pixels 12 and a pixel matrix 45 having both active matrix (AM) self-capacitive touch pixels and active thermal fingerprint sensor pixels. A TFT 11 is used to drive the display pixels 12, and a TFT 13 is used to drive pixels for the AM self-capacitive touch pixels and / or active thermal sensing pixels.

[0176] Figures 8A-8B show another embodiment of the FoD structure of this disclosure, in which an active matrix self-capacitive touch sensor and a fingerprint sensor are integrated into the display structure itself by a so-called in-cell FoD approach. Display pixels 12, such as side-by-side top-emitting OLED or micro-LED pixels, are integrated with active matrix self-capacitive touch sensing pixels and active thermal fingerprint sensing pixels 45 on the same glass substrate. TFT-based peripheral circuits for addressing the OLED or micro-LED emitter pixels and the self-capacitive touch sensing and active thermal fingerprint sensing pixels can be employed to minimize connections to external application-specific integrated circuits. The TFTs for the in-pixel TFTs (at least two TFTs in each emitter sub-pixel and one TFT in each self-capacitive electrode pixel) and peripheral circuits can be based on transparent oxide semiconductors (such as IGZO) or opaque LTPS TFTs.

[0177] Referring to Figures 8A-8B, TFTs based on transparent oxide semiconductors or opaque LTPS can be used for display and self-capacitive pixels. The self-capacitive pixel electrodes can be TCO or metal.

[0178] Figures 9A to 9C show sizable and resolution-configurable capacities and thermal scan steps according to several embodiments.

[0179] Figures 9A-9B illustrate other embodiments of the present disclosure in which the FoD system positions and selectively scans only the relevant fingerprint area to save scan time and power while simultaneously reducing MCU memory and processing overhead. Specifically, a capacitive and thermal scan with configurable size and resolution can be performed in the following steps: 1. Initial finger detection by high-speed capacitive scan: Identify and position the finger contact location by a full-screen coarse grid capacitive scan. 2. High-speed pre-scan: Small-area coarse grid active thermal scan or active matrix self-capacitive scan to confirm the contact location and determine the detailed scan boundary. 3. Detailed fingerprint scan: Small-area dense grid active thermal scan, combined with active matrix self-capacitive scan as an option to obtain a high-quality fingerprint image.

[0180] The examples shown in Figures 1-9 are intended to demonstrate the principles embodied in this disclosure. Various modifications and alterations to the embodiments selected for illustrative purposes are readily conceivable to those skilled in the art. To the extent that such modifications and alterations do not deviate from the spirit of this disclosure, it is intended that such modifications and alterations are included within the scope of this disclosure, and that such modifications and alterations are evaluated solely by a fair interpretation of the following claims. For example, the term “sensor substrate” is used in the drawings to indicate a common substrate material suitable for a TFT manufacturing process, but it encompasses hard glass or flexible substrate materials (such as polyimide).

[0181] As shown in Figures 3-6, in situations where transparency of the sensor substrate is required, the polyimide (PI) substrate can be made of a transparent type of PI material. After the manufacturing process of the touch / fingerprint sensor is completed, the PI film can be peeled from the carrier glass and, as shown in Figures 3 and 5, laminated directly onto the display or first laminated onto another transparent support substrate such as polyethylene terephthalate (PET) before being laminated onto the display.

[0182] In other scenarios, as shown in Figures 7-8, hard glass or flexible substrate materials (including both transparent and opaque PI films) can be used as "display and sensor substrates." To realize a flexible fingerprint sensor for a display device, the PI film is peeled from the carrier glass at the end of the fingerprint sensor manufacturing process and then laminated onto another flexible support substrate such as polyethylene terephthalate (PET).

[0183] Figures 3-6 show touch sensors and fingerprint sensors integrated into a display. As will be apparent to those skilled in the art, these independent touch sensors and fingerprint sensors can function independently even without a display, and these independent touch sensors and fingerprint sensors have the additional advantages of a larger area and higher resolution, as well as flexibility. This is because the touch sensors and fingerprint sensors can be manufactured on conventional sheet-to-sheet TFT fabs, on rigid mother glass, or on polyimide films coated or laminated on rigid mother glass, and can be peeled off after the sensor manufacturing process is complete and laminated onto other flexible substrates.

[0184] In independent touch sensor and fingerprint sensor application scenarios, transparency requirements for the sensor substrate, sensor array, and top hard coat can be relaxed. For example, additional non-oxide materials such as silicon carbide, tin selenide, tantalum nitride, or polysilicon can be used to form thermistors or diodes for active thermal fingerprint sensor pixels, and opaque materials such as DLC and SiC can be used to form the hard coat layer. While OLED and microLED are used as examples of light-emitting display elements in Figures 7 and 8, other types of light-emitting elements such as electroluminescent quantum dots or quantum dot light-emitting diodes (QLEDs) and inorganic electroluminescent devices can also be used. Figure 7 shows orthogonal rectangular electrodes as the upper and lower electrodes for mutual capacitance touch, but other shapes and configurations commonly used for mutual capacitance touch electrodes can also be used. Similarly, while rectangular scan boundaries are shown in steps 2 and 3 of Figure 9, this is for illustrative purposes only. The actual scan boundary can be any shape that freely adapts regularly or irregularly to the shape and size of the contacting finger.

[0185] Each sensor or device described herein may have other components such as ASICs, MCUs, display drive ICs, and PCBs, as shown in Figures 3 and 5. Through the MCU, the sensor or device, or a system including such a sensor or device, is configured to perform functions and steps for sensing and display. For example, the steps include detecting the presence of an object having a biometric pattern on the sensor; performing a coarse scan by scanning a portion of pixels in the pixel array to determine the contact boundary between the object and the sensor; and performing a selective fine scan within the contact boundary to provide image data of the biometric pattern. The steps may include rolling and positioning, image merging, and image data processing and comparison steps as described herein.

[0186] In some embodiments, the biometric sensor is a fingerprint sensor, the target is a finger, and the biometric pattern is a fingerprint. In some embodiments, the biometric pattern is on the palm, and the sensor or device is for detecting the pattern on the palm.

[0187] In other embodiments, the Disclosure provides a method for manufacturing a sensor, apparatus, or system comprising a sensor or apparatus as described herein. The method may include steps of forming each layer based on structure, or it may include steps of film deposition and etching.

[0188] In other embodiments, the Disclosure provides a method of using an apparatus or system. Such a method comprises the steps of: detecting the presence of an object having a biometric pattern on a sensor; performing a coarse scan (pre-scan) by scanning a portion of the pixels of a pixel array to determine the contact boundary between the object and the sensor; and performing a selective fine scan within the contact boundary to provide image data of the biometric pattern.

[0189] In such a method, the presence of an object, such as a finger touching the sensor, is detected via a thermal sensing pixel or a capacitive sensing node. Coarse and detailed scans are performed via the thermal sensing pixel.

[0190] Such a method may include dynamically tracking the rolling motion and position of an object by capacitive scanning using a capacitive sensing node. The method may further include one or more steps of combining biometric images of the object acquired by thermal scanning during the object's rolling motion using an MCU to provide a complete biometric pattern.

[0191] In some embodiments, the capacitance sensing node is either a mutual capacitance sensing node or a self-capacitance sensing node. The self-capacitance sensing node is either passively matrix-addressed or actively matrix-addressed by a thin-film transistor array. The mutual capacitance sensing node is configured to be passively matrix-addressed.

[0192] Each pixel array described herein comprises a sensor element or pixel, such as a thermal sensing pixel (as illustrated). The pixel array may be a two-dimensional network of pixels. In some embodiments, the pixel or sensor element may have one or more diodes connected in series between the pixel rows and the pixel columns. The diodes are in close proximity to the sensor surface and in good thermal contact with the fingerprint being measured, and may serve as both a pixel heater and a temperature sensing element.

[0193] The heating power of a pixel is proportional to the product of the number of diodes and the predetermined current and voltage applied to each diode. Diodes are temperature sensitive, and when the current is biased, a change in the pixel's temperature reflects a corresponding change in voltage, or when the voltage is biased, a change in the pixel's temperature reflects a corresponding change in current.

[0194] The pixel diode can be any microelectronic device structure having pure rectification characteristics or composite rectification characteristics. Suitable diode examples include, but are not limited to, PN junction rectifiers, Schottky rectifiers, PIN diodes, or any combination thereof. The diode may be made of a compound semiconductor such as SiGe, a metal or organic material such as aluminum and its alloys having suitable properties. The atomic structure may be single crystal, amorphous or polycrystalline.

[0195] The pixels may be covered with a conductive or semiconductor layer (not shown) that can be grounded to shield and protect the sensor. A protective coating (not shown) may be applied on top of the conductive or semiconductor layer to provide mechanical and chemical protection during use.

[0196] Referring, for example, to Figures 9A-9C, the exemplary method comprises at least three steps. The first step is to detect the presence of an object having a biometric pattern on the sensor. The second step is to perform a coarse scan by scanning a portion of the pixels of the pixel array to determine the contact boundary between the object and the sensor. The third step is to perform a selective fine scan within the contact boundary to provide image data of the biometric pattern.

[0197] In the first step, during standby mode, the sensing system periodically performs an initial scan to detect the presence or absence of finger contact on the sensor, for example, by performing a capacitive scan using a low-resolution capacitive sensing grid. Only a small fraction of pixels, evenly distributed across the sensor's pixel array, are selected to detect a finger. Once finger contact is detected and stable contact of the finger with the sensor is confirmed, the system moves to the next pre-scan (coarse thermal scan) stage, selecting a further set of pixels around the identified finger contact area to determine the fingerprint boundary. The system may select an even larger proportion of pixels around the identified contact area to improve the accuracy of boundary calculations. Subsequently, a thermal scan at maximum resolution (i.e., fine thermal) is performed to collect a detailed fingerprint image within the identified boundary. The fingerprint scan area is only a small fraction of the entire pixel array.

[0198] One technique to improve image quality and signal-to-noise ratio (SNR) is to average multiple images of the same fingerprint region to generate the final image.

[0199] Referring to Figures 10A to 10D, four exemplary thin-film transistors (TFTs) used in an exemplary device are shown. The TFTs may be used in an active thermal fingerprint sensor. The TFT has a source region, a drain region, and a channel. The channel includes or is composed of an oxide semiconductor material. The oxide semiconductor material may be a metal oxide such as IGZO and modified IGZO as described herein. The TFT may further include a substrate, a gate, a gate insulating layer, and an etching stop layer.

[0200] Figure 10A shows a TFT with the gate positioned on the bottom and the source / drain region, channel, and etching stop layer positioned on the top. The oxide semiconductor layer (channel) is located below the source / drain region and above the gate.

[0201] Figure 10B shows a TFT with the gate positioned at the top and the source / drain region at the bottom. The oxide semiconductor layer (channel) is located between the source / drain region.

[0202] Figure 10C shows a TFT with the gate located at the bottom and the source / drain region at the top. The oxide semiconductor layer (channel) is located between the source / drain region and the gate.

[0203] Figure 10D shows a self-aligned TFT with the gate positioned at the top and the source / drain region at the bottom. The oxide semiconductor layer (channel) is located between the source / drain region.

[0204] The source / drain region material of a TFT containing an oxide semiconductor material such as IGZO or modified IGZO is a metal or a transparent conductor such as ITO or other transparent conductive oxide (TCO). A two-terminal diode using an oxide semiconductor is a Schottky diode formed by depositing metals with different work functions, such as molybdenum (Mo), titanium (Ti), nickel (Ni), platinum (Pt), or gold (Au), at both ends of an oxide semiconductor channel. Since oxide semiconductors are usually n-type, an asymmetric structure is obtained that achieves IV characteristics for rectification by depositing a metal with a low work function at one end of the oxide semiconductor channel to form an ohmic contact and a metal with a high work function at the other end to form a Schottky contact. In some embodiments, the TFT also functions as a diode when the drain region and gate of a TFT containing an oxide semiconductor such as IGZO or modified IGZO are connected. A thin-film thermistor is a two-terminal passive thin-film device that does not necessarily have to be TFT-based. Thin-film thermistors are formed by depositing thin films of the same type of metal, such as Pt, Au, Ti / TiN, Ni, Cr, Al, or Mo, on both ends of an oxide semiconductor channel. IGZO, ZNO, Mn3O4, Co3O4, and NiO are examples of oxide semiconductors used in NTC (negative temperature coefficient) thin-film oxide thermistors.

[0205] Devices such as in-cell or out-cell biometric sensors in display devices offer excellent anti-spoofing capabilities. For example, in some embodiments, capacitive touch sensing elements are active-matrix self-capacitive touch sensors used in combination with active thermal sensing to improve anti-spoofing performance. As another example, thermal sensing pixels include pixels for passive thermal sensing used in combination with active thermal sensing to improve anti-spoofing performance.

[0206] Table 1 summarizes some examples of biometric sensors, such as fingerprint sensors, and biometric on-display (SoD) devices, such as fingerprint on-display (FoD) devices, having combinations of structures and features described herein. Table 1 is illustrative for illustrative purposes only and does not exhaust all possible combinations. In Table 1, the abbreviations "AM" and "PM" refer to active matrix and passive matrix, respectively. The term "sensor" refers to a biometric sensor. The term "SoD device" refers to a biometric on-display device. The term "micro-T sensor" refers to a micro-temperature sensor within a pixel.

[0207] [Table 1]

[0208] As shown in Table 1, in some preferred embodiments, the capacitive touch sensing element is an active-matrix (AM) self-capacitive touch sensor used in combination with active thermal sensing to improve anti-spoofing performance. In some other preferred embodiments, anti-spoofing performance can be improved by using a combination of passive and active thermal sensing. Examples of these with excellent anti-spoofing performance include, but are not limited to, Examples S3, S4, S5, S6, S9, S10, S11, S12, S13, S14, S17, S18, S19, S20, S21 and S22 shown in Table 1. The active-matrix (AM) self-capacitive touch sensor can be used, for example, to perform high-resolution scanning in “fingerprint mode” to improve anti-spoofing performance. Devices such as Examples S14 and S22 are even more preferred. When scanning with an AM self-capacitive touch sensor at high resolution (“fingerprint mode”), Examples S14 and S22 provide the best anti-spoofing performance by using three separate fingerprint sensing modes. These modes include active thermal sensing, passive thermal sensing, and AM self-capacitance sensing.

[0209] This disclosure provides systems comprising each of the sensors or devices described herein. The sensors, devices, systems, and methods provided herein offer significant advantages not available in existing technologies. For example, the sensors and devices provided herein enable large-area, high-resolution biometric sensing and can be combined with displays. They offer excellent anti-impersonation performance, as demonstrated by extremely low false positive rates (FRR) and false rejection rates (FAR).

[0210] The methods and systems described herein may be implemented, at least in part, in the form of computer implementation processes and apparatus for performing the process. The disclosed methods may be implemented, at least in part, in the form of a tangible, non-temporary, machine-readable storage medium on which computer program code is encoded. The medium may include, for example, RAM, ROM, CD-ROM, DVD-ROM, BD-ROM, hard disk drive, flash memory, other non-temporary, machine-readable storage media, or any combination thereof, and when the computer program code is loaded into and executed by the computer, the computer becomes an apparatus for performing the method. The method may be implemented, at least in part, in the form of a computer on which the computer program code is loaded and / or executed. In this way, the computer becomes an apparatus for performing the method. When implemented in a general-purpose processor, the computer program code segments constitute the processor to create specific logic circuits. Alternatively, the method may be implemented, at least in part, in a digital signal processor (DSP) consisting of an application-specific integrated circuit (ASIC) for performing the method.

[0211] While the subject matter has been described in relation to exemplary embodiments, it is not limited thereto. Rather, the appended claims should be interpreted broadly to include other variations and embodiments that may be implemented by those skilled in the art.

Claims

1. A pixel matrix having multiple pixels configured to measure a biometric authentication pattern, A micro-temperature sensor and a micro-heater are arranged within each pixel, wherein the micro-temperature sensor includes an oxide semiconductor material, A sensor for biometric authentication comprising, wherein the plurality of pixels include thermal sensing pixels configured to operate on at least an active thermal sensing principle, and a low-power thermal pulse is applied to the thermal sensing pixels and a response corresponding to a biometric authentication pattern is measured.

2. The sensor according to claim 1, wherein the microheater includes the oxide semiconductor material or the conductive material.

3. The sensor according to claim 2, wherein the conductive material is selected from the group consisting of metal, transparent conductive film (TCO), and combinations thereof.

4. The sensor according to claim 1, wherein the oxide semiconductor material includes indium gallium zinc oxide (IGZO) or modified IGZO.

5. The sensor according to claim 4, wherein the modified IGZO comprises an element selected from the group consisting of aluminum (Al), tin (Sn), titanium (Ti), tungsten (Ta), zirconium (Zr), cobalt (Co), nickel (Ni), hafnium (Hf), silicon (Si), fluorine (F), germanium (Ge), yttrium (Y), radium (La), and any combination thereof, which may partially or completely replace existing cations in the IGZO or function as additional cations.

6. The sensor according to claim 4, wherein the IGZO or modified IGZO is amorphous or crystalline.

7. The sensor according to claim 1, wherein the oxide semiconductor material has a temperature coefficient in the range of -2 mV / °C to -200 mV / °C.

8. The sensor according to claim 1, wherein the oxide semiconductor material has a sheet resistance in the range of 5 kΩ / sq to 3 MΩ / sq.

9. The sensor according to claim 1, wherein each of the micro-temperature sensor and the micro-heater is a thin-film transistor (TFT), a diode, or a thermistor.

10. The sensor according to claim 1, wherein the micro-temperature sensor and the micro-heater are integrated into a single device at each pixel.

11. The sensor according to claim 1, wherein the micro-temperature sensor and the micro-heater are separated in each pixel, and the micro-heater is part of a plurality of micro-heater lines.

12. The sensor according to claim 1, further comprising a capacitive touch sensing element.

13. The sensor according to claim 12, wherein the capacitive touch sensing element is self-capacitive or mutually capacitive and is an active matrix or a passive matrix.

14. The sensor according to claim 12, wherein the capacitive touch sensing element is a passive matrix mutual capacitive touch sensor or an active matrix self-capacitive touch sensor.

15. The sensor according to claim 14, wherein the capacitive touch sensing element is an active matrix self-capacitive touch sensor used in combination with active thermal sensing to improve anti-impersonation performance.

16. The sensor according to claim 1, wherein the thermal sensing pixel includes a pixel that performs passive thermal sensing in combination with active thermal sensing in order to improve the anti-impersonation performance.

17. An apparatus or system comprising the sensor described in claim 1.

18. A method for manufacturing the sensor according to claim 1, comprising forming a pixel matrix having a plurality of pixels, each of which has the micro-temperature sensor and the micro-heater.

19. A method using the sensor according to claim 1, comprising the step of measuring or acquiring an image of a subject's biometric authentication pattern.

20. The method according to claim 19, wherein the biometric authentication pattern is a fingerprint or a palm pattern.

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