Tactile sensor array based on silicon-based Micro LED and its preparation method

Abstract

The present invention provides a tactile sensor array based on silicon-based MicroLED and a preparation method thereof, wherein the tactile sensor array includes regularly distributed tactile sensor device units, which are used to realize the tactile sensing function, and the distribution density thereof determines the resolution of the tactile sensor. The present invention adopts a silicon-based epitaxial wafer to reduce the direct coupling of light, which is beneficial to reducing the background noise of the sensor; by using MEMS process technology, the device finally obtained is small in size and light in weight, and the production cost can be reduced through mass production, which is beneficial to the application and promotion of the present invention; based on the principle of photoelectric detection, the tactile sensor array of the present invention has the advantages of high resolution and sensitivity, fast response speed and strong anti-electromagnetic interference ability; the size of the tactile sensor array of the present invention can be scaled according to the process capability of the preparation, and through large-scale and high-density integration, a high-resolution tactile sensing function can be realized.

Description

Technical Field

[0001] The present invention relates to the technical field of micro-electromechanical systems, and in particular to a tactile sensor array based on silicon-based Micro LEDs and a preparation method thereof. Background Art

[0002] Touch is an important way for organisms to perceive information from the outside world. Tactile sensors are devices that measure information generated from physical interactions with its environment. Tactile sensors are usually modeled on the biological sense of skin contact, which can detect stimuli caused by mechanical stimulation, temperature, and pain (although pain sensing is not common in artificial tactile sensors).

[0003] Tactile sensors are sensors used in robots to mimic the sense of touch, computer hardware and security systems. Tactile sensors are commonly used in touch screen devices on mobile phones and computers. In recent years, the surging demand for the application of intelligent robots in the fields of medicine, home appliances, manufacturing, food and transportation has promoted the research and development of new tactile sensors. Photoelectric tactile sensors have the advantages of high sensitivity, fast response speed and strong anti-electromagnetic interference ability. Combined with advanced MEMS manufacturing technology, it has become possible to integrate the various components of photoelectric tactile sensors on a chip, thereby realizing the miniaturization and arraying of tactile sensors, which is conducive to improving the perception resolution. In addition, integrating more functions on the tactile sensor chip based on compatible processes is in line with the future development trend of sensors.

[0004] In view of the above, it is necessary to provide a tactile sensor array based on silicon-based Micro LED and a preparation method thereof to meet the requirements of tactile sensor arraying and high-density integration and effectively improve the perception resolution of the tactile sensor. Summary of the invention

[0005] In view of the shortcomings of the prior art mentioned above, the object of the present invention is to provide a tactile sensor array based on silicon-based Micro LED and a preparation method thereof, so as to meet the requirements of tactile sensor arraying and high-density integration, and effectively improve the perception resolution of the tactile sensor.

[0006] To achieve the above-mentioned object and other related objects, the present invention provides a tactile sensor array based on silicon-based Micro LEDs, wherein the tactile sensor array based on silicon-based Micro LEDs comprises: tactile sensor device units that are regularly distributed;

[0007] The tactile sensor device unit includes two Micro LEDs, one of which is used as a Micro LED light source, and the other is used as a Micro LED detector;

[0008] The Micro LED light source comprises:

[0009] A light source active layer, which includes, from bottom to top, a light source P-type GaN layer, a light source multi-quantum well layer, and a light source N-type GaN layer;

[0010] A light source positive electrode, located below the light source P-type GaN layer;

[0011] A light source negative electrode, directly in contact with the lower portion of the light source N-type GaN layer, and having a gap between the platforms formed by the light source P-type GaN layer and the light source multi-quantum well layer;

[0012] A planarized dielectric layer covering below the light source positive electrode (8) and the light source negative electrode (9);

[0013] A light source positive bonding electrode (10) is located below the light source positive electrode, the light source positive bonding electrode comprises two parts, a columnar part passes through the planarized dielectric layer, and the other part covers the surface of the planarized dielectric layer;

[0014] A light source negative bonding electrode, located below the light source negative electrode, the light source negative bonding electrode comprises two parts, a columnar part passes through the planarized dielectric layer, and the other part covers the surface of the planarized dielectric layer;

[0015] The light source non-intentionally doped GaN layer and the light source material buffer layer are sequentially located above the light source N-type GaN layer;

[0016] The Micro LED detector has the same structure as the Micro LED light source, and the Micro LED detector is located on the side of the Micro LED light source;

[0017] The tactile sensor device unit also includes:

[0018] a silicon substrate layer, located above the light source material buffer layer and the detector material buffer layer, wherein two through holes are arranged on the silicon substrate layer, respectively located above the two Micro LED active layers, wherein one of the through holes exposes the Micro LED light source, and the other through hole exposes the Micro LED detector, and part of the light emitted by the Micro LED light source (3) is reflected by the reflective layer (30) onto the Micro LED detector (4);

[0019] A light-transmitting layer, the light-transmitting layer is used to fill the through hole on the silicon substrate layer and cover the upper surface of the silicon substrate layer;

[0020] The visible light reflecting layer and the contact protection layer are sequentially located above the light transmitting layer.

[0021] Optionally, the tactile sensor device unit is bonded to a substrate via substrate bonding metal, and a circuit unit is contained on the surface or inside of the substrate, and the circuit unit is used to process and analyze the output signal of the Micro LED.

[0022] Optionally, an isolation groove is provided between the Micro LED light source and the Micro LED detector, and isolation metal is provided in the isolation groove.

[0023] Optionally, the silicon-based Micro LED-based tactile sensor array further includes pulse sensor device units, the number of the pulse sensor device units is less than the tactile sensor device units, and the pulse sensor device units are orderly distributed in the tactile sensor array; the structure of the pulse sensor device unit is different from that of the tactile sensor device unit in that the pulse sensor device unit does not include the visible light reflecting layer in the tactile sensor device unit.

[0024] Optionally, the pulse sensor device unit is bonded to the substrate through the substrate bonding metal, and the surface or interior of the substrate contains a circuit unit, and the circuit unit is used to process and analyze the output signal of the Micro LED.

[0025] Optionally, the maximum width of the multi-quantum well layer of the light source is less than 100 μm.

[0026] Optionally, the through hole arranged on the silicon substrate layer is larger at the top and smaller at the bottom, and the cross-sectional shape of the through hole is rectangular or circular.

[0027] Optionally, the material of the visible light reflecting layer is metal Ag, and the material of the contact protection layer is resin.

[0028] The present invention also provides a method for preparing a tactile sensor array based on silicon-based Micro LEDs, the preparation method comprising:

[0029] S1: Providing a silicon-based gallium nitride LED epitaxial wafer, wherein the silicon-based gallium nitride LED epitaxial wafer comprises, from bottom to top, a silicon substrate, a material buffer layer, an unintentionally doped GaN material layer, an N-type GaN material layer, a multi-quantum well material layer, and a P-type GaN material layer;

[0030] S2: Photolithography and etching are performed on the front side of the silicon-based gallium nitride LED epitaxial wafer until the silicon substrate is reached, so as to form isolation grooves between different regions. Photolithography and etching are performed on the front side of the silicon-based gallium nitride LED epitaxial wafer until the N-type GaN layer is reached, so as to form active layers of different Micro LEDs together with the N-type GaN layer.

[0031] S3: forming a positive electrode of the Micro LED on the front side of the silicon-based gallium nitride LED epitaxial wafer;

[0032] S4: forming a negative electrode of the Micro LED on the front side of the silicon-based gallium nitride LED epitaxial wafer;

[0033] S5: forming the planarized dielectric layer on the front side of the silicon-based gallium nitride LED epitaxial wafer, opening holes to form columnar portions of the positive bonding electrode and the negative bonding electrode, and then forming complete positive bonding electrodes and negative bonding electrodes on the surface of the planarized dielectric layer;

[0034] S6: inverting the above structure, photolithography and etching the through hole on the silicon substrate to form a silicon substrate layer;

[0035] S7: coating a light-transmitting material higher than the silicon substrate layer on the surface of the structure and in the through hole to form the light-transmitting layer;

[0036] S8: forming the visible light reflecting layer and the contact protection layer in sequence above the light-transmitting layer.

[0037] Optionally, in step S6, after forming the positive bonding electrode and the negative bonding electrode, the step of bonding the obtained structure to a substrate through a substrate bonding metal is also included, and the surface or interior of the substrate contains a circuit unit, and the circuit unit is used to process and analyze the output signal of the Micro LED.

[0038] As described above, the tactile sensor array based on silicon-based Micro LED and the preparation method thereof of the present invention have the following beneficial effects: 1. The tactile sensor array based on silicon-based Micro LED of the present invention adopts silicon-based epitaxial wafers, so that the direct coupling of light is reduced, which is beneficial to reducing the background noise of the sensor; 2. The tactile sensor array based on silicon-based Micro LED of the present invention utilizes MEMS process technology, and the final device is small in size and light in weight, and the production cost can be reduced through mass production, which is beneficial to the application and promotion of the present invention; 3. Based on the principle of photoelectric detection, the tactile sensor array of the present invention has the advantages of high resolution and sensitivity, fast response speed and strong anti-electromagnetic interference ability; 4. The size of the tactile sensor array of the present invention can be scaled according to the process capability of the preparation, and through large-scale and high-density integration, high-resolution tactile sensing function can be achieved. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 Shown is a schematic structural diagram of a tactile sensor array based on silicon-based Micro LEDs of the present invention.

[0040] Figure 2 It is a cross-sectional schematic diagram of a touch sensor device unit of the present invention.

[0041] Figure 3 to Figure 4 It is a schematic diagram showing the working principle of the tactile sensor device unit of the present invention.

[0042] Figure 5 It is a schematic cross-sectional view of a pulse sensor device unit of the present invention.

[0043] Figure 6 to Figure 7 It is a schematic diagram showing the working principle of the pulse sensor device unit of the present invention.

[0044] Figure 8 It is a schematic cross-sectional view taken along the line AA′ of a tactile sensor device unit when the through hole in the silicon substrate layer of the present invention is rectangular.

[0045] Fig. 9 It is a schematic cross-sectional view taken along the line AA′ of a tactile sensor device unit when the through hole in the silicon substrate layer of the present invention is circular.

[0046] Fig.10 Shown is a schematic flow chart of a method for preparing a tactile sensor array based on silicon-based Micro LEDs of the present invention.

[0047] Figures 11 to 19 Shown is a schematic structural diagram of each step of the method for preparing a tactile sensor array based on silicon-based Micro LEDs of the present invention.

[0048] Component number description

[0049] 100 Silicon substrate

[0050] 200 Material buffer layer

[0051] 300 Unintentionally doped GaN material layer

[0052] 400 N-type GaN material layer

[0053] 500 Multi-Quantum Well Material Layers

[0054] 600 P-type GaN material layer

[0055] 1 Tactile sensor device unit

[0056] 2 Pulse sensor device unit

[0057] 3 Micro LED light source

[0058] 4 Micro LED Detector

[0059] 5 Light source P-type GaN layer

[0060] 6 Light source multi-quantum well layer

[0061] 7 Light source N-type GaN layer

[0062] 8 Light source positive electrode

[0063] 9 Light source negative electrode

[0064] 10 Light source positive bonding electrode

[0065] 11 Light source negative bonding electrode

[0066] 12 The light source is not intentionally doped with GaN layer

[0067] 13 Light source material buffer layer

[0068] 14 Detector P-type GaN layer

[0069] 15 Detector Multi-Quantum Well Layer

[0070] 16 Detector N-type GaN layer

[0071] 17 Detector positive electrode

[0072] 18 Detector negative electrode

[0073] 19 Detector positive bonding electrode

[0074] 20 Detector negative bonding electrode

[0075] 21. Planarization dielectric layer

[0076] 22 substrate

[0077] 23 Substrate bonding metal

[0078] 24 Through-hole Metal

[0079] 25 Circuit Units

[0080] 26 Detector unintentionally doped GaN layer

[0081] 27 Detector material buffer layer

[0082] 28 Silicon substrate layer

[0083] 29 Translucent Layer

[0084] 30 Visible light reflection layer

[0085] 31 Contact protection layer

[0086] 32 Skin

[0087] 33 Isolation Metal

[0088] 34 Light DETAILED DESCRIPTION

[0089] The following describes the embodiments of the present invention through specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention.

[0090] See also Figures 1 to 19 It should be noted that the illustrations provided in this embodiment are only used to illustrate the basic concept of the present invention in a schematic manner, and the illustrations only show components related to the present invention rather than being drawn according to the number, shape and size of components in actual implementation. In actual implementation, the type, quantity and proportion of each component may be changed arbitrarily, and the component layout may also be more complicated.

[0091] Embodiment 1

[0092] like Figure 1 to Figure 2 As shown, this embodiment provides a tactile sensor array based on silicon-based Micro LED (such as Figure 1 As shown), the silicon-based Micro LED tactile sensor array includes: regularly distributed tactile sensor device units 1 (as shown Figure 1 and Figure 2 shown);

[0093] The tactile sensor device unit 1 includes two Micro LEDs, one of which is used as a Micro LED light source 3, and the other is used as a Micro LED detector 4 (such as Figure 2 shown);

[0094] The Micro LED light source 3 includes:

[0095] A light source active layer, which includes, from bottom to top, a light source P-type GaN layer 5, a light source multi-quantum well layer 6, and a light source N-type GaN layer 7;

[0096] A light source positive electrode 8, located below the light source P-type GaN layer 5;

[0097] The light source negative electrode 9 is in direct contact with the lower side of the light source N-type GaN layer 7 and has a gap between the platforms formed by the light source P-type GaN layer 5 and the light source multi-quantum well layer 6;

[0098] A planarized dielectric layer 21, covering below the light source positive electrode 8 and the light source negative electrode 9;

[0099] The light source positive bonding electrode 10 is located below the light source positive electrode 8. The light source positive bonding electrode 10 includes two parts, a columnar part that penetrates the planarization dielectric layer 21, and another part that covers the surface of the planarization dielectric layer 21;

[0100] The light source negative bonding electrode 11 is located below the light source negative electrode 9. The light source negative bonding electrode 9 includes two parts, a columnar part that penetrates the planarization dielectric layer 21, and another part that covers the surface of the planarization dielectric layer 21;

[0101] The light source non-intentionally doped GaN layer 12 and the light source material buffer layer 13 are sequentially located above the light source N-type GaN layer 7;

[0102] The Micro LED detector 4 has the same structure as the Micro LED light source 3, and the Micro LED detector 4 is located on the side of the Micro LED light source 3; specifically, the Micro LED detector 4 includes:

[0103] A detector active layer, which includes, from bottom to top, a detector P-type GaN layer 14, a detector multi-quantum well layer 15, and a detector N-type GaN layer 16;

[0104] A detector positive electrode 17, located below the detector P-type GaN layer 14;

[0105] A detector negative electrode 18, directly in contact with the bottom of the detector N-type GaN layer 16, and having a gap between the platform formed by the detector P-type GaN layer 14 and the detector multi-quantum well layer 15;

[0106] A planarized dielectric layer 21, covering below the detector positive electrode 17 and the detector negative electrode 18;

[0107] The detector positive bonding electrode 19 is located below the detector positive electrode 17. The detector positive bonding electrode 17 includes two parts, a columnar part that penetrates the planarization dielectric layer 21, and another part that covers the surface of the planarization dielectric layer 21;

[0108] The detector negative bonding electrode 20 is located below the detector negative electrode 18. The detector negative bonding electrode 20 includes two parts, a columnar part that penetrates the planarized dielectric layer 21, and another part that covers the surface of the planarized dielectric layer 21;

[0109] The detector non-intentionally doped GaN layer 26 and the detector material buffer layer 27 are sequentially located above the detector N-type GaN layer 16;

[0110] The tactile sensor device unit 1 further includes:

[0111] A silicon substrate layer 28 is located above the light source material buffer layer 13 and the detector material buffer layer 27. Two through holes are provided on the silicon substrate layer 28, which are respectively located above the active layers of the two Micro LEDs. One of the through holes exposes the Micro LED light source 3, and the other through hole exposes the Micro LED detector 4. Part of the light emitted by the Micro LED light source 3 is reflected by the reflective layer 30 to the Micro LED detector 4.

[0112] A light-transmitting layer 29, the light-transmitting layer 29 is used to fill the through hole of the silicon substrate layer 28 and cover the upper surface of the silicon substrate layer 28;

[0113] The visible light reflection layer 30 and the contact protection layer 31 are sequentially located above the light-transmitting layer 29. The tactile sensor array based on silicon-based Micro LED uses silicon-based epitaxial wafers to reduce direct coupling of light, which is beneficial to reducing the background noise of the sensor; using MEMS process technology, the final device is small in size and light in weight, and can reduce production costs through mass production, which is beneficial to the application and promotion of the present invention; the tactile sensor array based on silicon-based Micro LED is based on the principle of photoelectric detection, and has the advantages of high resolution and sensitivity, fast response speed and strong anti-electromagnetic interference ability; the size of the tactile sensor array based on silicon-based Micro LED can also be scaled according to the manufacturing process capability, and through large-scale and high-density integration, high-resolution tactile sensing function can be achieved.

[0114] The Micro LED detector 4 has the same structure as the Micro LED light source 3 , and their sizes and shapes may be the same or different, and may be set according to the performance of the tactile sensor array, which is not limited here.

[0115] The Micro LED light source 3 and the Micro LED detector 4 of this embodiment use the same multi-quantum well PN junction, and its physical mechanism is that the emission spectrum and detection of the multi-quantum well PN junction have overlapping areas. When the Micro LED light source 3 emits light, the Micro LED light source 3 is loaded with a forward bias, that is, the voltage of the positive electrode 8 of the light source is higher than that of the negative electrode 9 of the light source, and the P-type GaN layer 5 of the light source and the N-type GaN layer 7 of the light source respectively inject holes and electrons into the multi-quantum well layer 6 of the light source. Since the multi-quantum well has a limiting effect on holes and electrons, holes and electrons will be concentrated in the multi-quantum well layer 6 of the light source for radiation recombination, and emit light of a wavelength corresponding to the multi-quantum well structure. By adjusting the width or height of the multi-quantum well barrier or potential well, the central wavelength of the Micro LED light source 3 can be changed.

[0116] When the Micro LED detector 4 detects the intensity of the visible light signal, the Micro LED detector 4 is loaded with reverse bias or zero bias, that is, the voltage of the positive electrode 17 of the detector is lower than or equal to the negative electrode 18 of the detector, and some photogenerated carriers generated in the P-type GaN layer 14 of the detector, the multi-quantum well layer 15 of the detector and the N-type GaN layer 16 of the detector are effectively separated under the action of the electric field to form a photogenerated current. Since the photogenerated current is related to the intensity of the visible light received by the Micro LED detector 4, the intensity of the visible light can be inferred by the size of the photogenerated current.

[0117] Based on the above, the working principle of the tactile sensor device unit 1 is as follows: part of the light 34 emitted by the Micro LED light source 3 uses the through hole on the silicon substrate layer 28 as a light channel, passes through the visible light reflection layer 30, and is reflected to the Micro LED detector 4. When there is no external force, the optical coupling ratio from the Micro LED light source 3 to the Micro LED detector 4 is fixed, and the photocurrent is also constant (such as Figure 3 When an external force is applied, the visible light reflecting layer 30 bends, and the bending amount is related to the applied external force. At the same time, due to the change in the reflection path, the optical coupling ratio from the Micro LED light source 3 to the Micro LED detector 4 changes, which eventually causes the photocurrent of the Micro LED detector 4 to change. The magnitude of the external force can be inferred from the change in the photocurrent (such as Figure 4 The tactile sensor device unit 1 is the main unit of the silicon-based Micro LED tactile sensor array, which is used to realize the tactile sensing function, and its distribution density determines the resolution of the tactile sensing. Figure 2 As shown, as an example, the tactile sensor device unit 1 is bonded to the substrate 22 through the substrate bonding metal 23. The surface or interior of the substrate 22 contains a circuit unit 25. The circuit unit 25 is used to process and analyze the output signal of the Micro LED. In this embodiment, it is mainly used to process and analyze the output signals of the Micro LED light source 3 and the Micro LED detector 4.

[0118] It should be noted here that the substrate bonding metal 23 is electrically connected to the light source positive electrode 8 and the light source negative electrode 9 of the Micro LED light source 3 and the detector positive electrode 8 and the detector negative electrode 9 of the Micro LED detector 4, respectively, and is bonded to the substrate 22. When the circuit unit 25 is located inside the substrate 22, it is also necessary to be electrically connected to the substrate bonding metal 23 through the through-hole metal 24 to electrically connect the tactile sensor device unit 1 to the circuit unit 25, so as to control the Micro LED light source 3 and the Micro LED detector 4 through the circuit unit 25.

[0119] like Figure 2 As shown, as an example, an isolation groove is provided between the Micro LED light source 3 and the Micro LED detector 4, and an isolation metal 33 is provided in the isolation groove. The isolation metal 33 is surrounded by a planarization dielectric layer 21 to reduce the optical crosstalk between the Micro LED light source 3 and the Micro LED detector 4 to avoid affecting the performance of the tactile sensor device unit 1.

[0120] like Figure 1 and Figure 5 As shown, as an example, the silicon-based Micro LED tactile sensor array further includes a pulse sensor device unit 2, the number of the pulse sensor device units 2 is less than the tactile sensor device unit 1, and they are orderly distributed in the tactile sensor array (such as Figure 1 The structure of the pulse sensor device unit 2 is different from that of the tactile sensor device unit 1 in that the pulse sensor device unit does not include the visible light reflecting layer (such as Figure 5As shown); Specifically, the pulse sensor device unit 2 includes two Micro LEDs, one of which is a Micro LED light source 3, and the other is a Micro LED detector 4; the Micro LED light source 3 includes: a light source active layer, the light source active layer includes a light source P-type GaN layer 5, a light source multi-quantum well layer 6 and a light source N-type GaN layer 7 from bottom to top; a light source positive electrode 8, located below the light source P-type GaN layer 5; a light source negative electrode 9, directly in contact with the light source N-type GaN layer 7 below, and having a gap between the platforms formed by the light source P-type GaN layer 5 and the light source multi-quantum well layer 6; a planarization dielectric layer 21, covering the light source positive electrode 8 and the light source negative electrode 9 below; a light source positive bonding electrode (10), located Below the light source positive electrode 8, the light source positive bonding electrode 10 includes two parts, a columnar part penetrates the planarized dielectric layer 21, and the other part covers the surface of the planarized dielectric layer 21; the light source negative bonding electrode 11 is located below the light source negative electrode 9, and the light source negative bonding electrode 9 includes two parts, a columnar part penetrates the planarized dielectric layer 21, and the other part covers the surface of the planarized dielectric layer 21; the light source non-intentionally doped GaN layer 12 and the light source material buffer layer 13 are sequentially located above the light source N-type GaN layer 7; the Micro The LED detector 4 has the same structure as the Micro LED light source 3, and the Micro LED detector 4 is located on the side of the Micro LED light source 3; the tactile sensor device unit 1 also includes: a silicon substrate layer 28, located above the light source material buffer layer 13, and the silicon substrate layer 28 is provided with through holes, the number of the through holes is 2, and they are respectively located above the active layers of the two Micro LEDs, one of the through holes can expose the Micro LED light source 3, and the other through hole exposes the Micro LED detector 4; a light-transmitting layer 29, the light-transmitting layer 29 is used to fill the through holes of the silicon substrate layer 28 and cover the upper surface of the silicon substrate layer 28; a contact protection layer 31, located above the light-transmitting layer 29.

[0121] The pulse sensor device unit 2 is used to detect the pulse signal of contact with the skin, and serves as an auxiliary function unit of the silicon-based MicroLED-based tactile sensor array; the silicon-based MicroLED-based tactile sensor array can not only realize tactile sensing, but also monitor the pulse signal of the skin. In addition, since the Micro LED of the pulse sensor device unit can emit light, it can be used as a status indicator.

[0122] The working principle of the pulse sensor device unit 2 is as follows: when the pulse sensor device unit 2 is not touched by the skin, most of the light 34 emitted by the Micro LED light source 3 is emitted to the outside of the chip through the through hole of the silicon substrate layer 28, and only a small amount of light 34 is scattered by the environment and returns to the Micro LED detector 4 (such as Figure 6 When the skin is touched, part of the light 34 will be reflected by the skin 32 and return to the Micro LED detector 4 area (as shown in FIG. Figure 7 As shown, since the reflectivity of the skin 32 to the incident light is affected by the contraction and relaxation of blood vessels, the reflected light carries pulse information, and the frequency or change curve of the pulse can be obtained through the photocurrent of the Micro LED detector 4.

[0123] like Figure 5 As shown, as an example, the pulse sensor device unit 2 is bonded to the substrate 22 through the substrate bonding metal 23, and the surface or interior of the substrate 22 contains a circuit unit 25, and the circuit unit 25 is used to process and analyze the output signals of the Micro LED light source 3 and the Micro LED detector 4.

[0124] It should be noted that, for the tactile sensor device unit 1 and the pulse sensor device unit 2 , the specific form of the circuit unit 25 may be different.

[0125] As an example, the maximum width of the light source multi-quantum well layer 6 is less than 100 μm.

[0126] It should be noted here that, in the light source active layer, the area of ​​the light source N-type GaN layer 7 is larger than the light source P-type GaN layer 5 and the light source multi-quantum well layer 6, and the light source P-type GaN layer 5 and the light source multi-quantum well layer 6 are platforms or protrusions on the light source N-type GaN layer 7 in terms of morphology.

[0127] like Figures 8 to 9 As shown, as an example, the through hole arranged on the silicon substrate layer 28 is larger at the top and smaller at the bottom, and the cross-sectional shape of the through hole is rectangular or circular. The through holes are respectively located directly above the light source multi-quantum well layer 6 and the detector multi-quantum well layer 15. The shapes of the through holes can be the same or different, and are selected according to actual conditions, and there is no limitation here.

[0128] As an example, the planarization dielectric layer 21 should be made of a dielectric material that has fluidity under specific conditions. In this embodiment, borophosphosilicate glass is preferably used. In addition, the lower surface of the planarization dielectric layer 21 needs to be relatively flat in the horizontal direction, so that the lower surfaces of the positive bonding electrode 10 of the light source and the negative bonding electrode 11 of the light source can be on the same horizontal line, which is beneficial to the bonding between the Micro LED light source 3 and the substrate 22; similarly, the lower surfaces of the positive bonding electrode 19 of the detector and the negative bonding electrode 20 of the detector can also be on the same horizontal line, which is beneficial to the bonding between the Micro LED detector 4 and the substrate 22; in addition, in this embodiment, the material of the substrate 22 is preferably single crystal silicon.

[0129] As an example, the light-transmitting layer 29 should have a certain degree of flexibility, and the upper surface of the light-transmitting layer 29 is relatively flat, which is conducive to the deposition of the visible light reflecting layer 30 above. In this embodiment, the material of the visible light reflecting layer 30 is preferably metal Ag. The contact protection layer 31 is used as the contact surface between the external force and the tactile sensor device unit 1 to protect the internal structure of the device. In this embodiment, the material of the contact protection layer 31 is preferably a resin material.

[0130] Embodiment 2

[0131] This embodiment provides a method for preparing a tactile sensor array based on silicon-based Micro LEDs. Fig.10 As shown, the preparation method can be used to prepare the silicon-based Micro LED tactile sensor array described in the first embodiment, such as Figures 11 to 18 As shown, the preparation method of the silicon-based Micro LED tactile sensor array according to the second embodiment is described in detail.

[0132] like Fig.10 and Fig.11 As shown, firstly, step S1 is performed to provide a silicon-based gallium nitride LED epitaxial wafer, wherein the silicon-based gallium nitride LED epitaxial wafer includes, from bottom to top, a silicon substrate 100, a material buffer layer 200, an unintentionally doped GaN material layer 300, an N-type GaN material layer 400, a multi-quantum well material layer 500, and a P-type GaN material layer 600. The silicon-based Micro LED tactile sensor array uses a silicon-based epitaxial wafer to reduce direct coupling of light, which is beneficial to reducing the background noise of the sensor.

[0133] like Fig.10 and Fig.12As shown, step S2 is then performed, in which photolithography and etching are performed on the front side of the silicon-based gallium nitride LED epitaxial wafer to stop at the silicon substrate 100 to form isolation grooves between different regions, and then photolithography and etching are performed on the front side of the silicon-based gallium nitride LED epitaxial wafer to stop at the N-type GaN layer 400 to form active layers of different Micro LEDs together with the N-type GaN layer 400.

[0134] It should be noted here that in this step, the light source material buffer layer 13, the light source unintentionally doped GaN layer 12, the light source N-type GaN layer 7, the light source multi-quantum well layer 6 and the light source P-type GaN layer 5 of the Micro LED light source 3, and the detector material buffer layer 27, the detector unintentionally doped GaN layer 26, the detector multi-quantum well layer 15 and the detector P-type GaN layer 14 of the Micro LED detector 4 are formed. Fig.12 In addition, in this step, after photolithography, inductively coupled plasma etching technology is used for etching.

[0135] like Fig.10 and Fig.13 As shown, step S3 is then performed to form a positive electrode of the Micro LED on the front side of the silicon-based gallium nitride LED epitaxial wafer.

[0136] It should be noted here that the positive electrode of the Micro LED formed includes the light source positive electrode 8 and the detector positive electrode 17; the light source positive electrode 8 is in direct contact with the light source P-type GaN layer 5, which is an ohmic contact, and the material of the light source positive electrode 8 is preferably a nickel-gold alloy in this embodiment; similarly, the detector positive electrode 17 is in direct contact with the detector P-type GaN layer 14, which is an ohmic contact, and the material of the detector positive electrode 17 is preferably a nickel-gold alloy in this embodiment.

[0137] As an example, the method of forming the light source positive electrode 8 and the detector positive electrode 17 is electron beam evaporation (EBE) deposition.

[0138] like Fig.10 and Fig.14 As shown, step S4 is then performed to form a negative electrode of the Micro LED on the front side of the silicon-based gallium nitride LED epitaxial wafer.

[0139] It should be noted here that the negative electrode of the Micro LED formed includes the light source negative electrode 9 and the detector negative electrode 18; the light source negative electrode 9 is also in ohmic contact with the light source N-type GaN layer 7, and the material of the light source negative electrode 9 is preferably titanium aluminum nickel gold alloy in this embodiment; the detector negative electrode 18 is also in ohmic contact with the detector N-type GaN layer 16, and the material of the detector negative electrode 18 is preferably titanium aluminum nickel gold alloy in this embodiment.

[0140] As an example, the method of forming the light source negative electrode 9 and the detector negative electrode 18 is also electron beam evaporation (EBE) deposition technology.

[0141] like Fig.10 and Fig.15 As shown, step S5 is then performed to form the planarized dielectric layer 21 on the front side of the silicon-based gallium nitride LED epitaxial wafer, and holes are opened to form the columnar parts of the positive bonding electrode and the negative bonding electrode, and then a complete positive bonding electrode and a negative bonding electrode are formed on the surface of the planarized dielectric layer 21.

[0142] It should be noted here that the bonding electrode includes a columnar portion penetrating the planarization dielectric layer 21 and a portion located on the surface of the planarization dielectric layer 21; the positive bonding electrode includes the light source positive bonding electrode 10 and the detector positive bonding electrode 19, and the negative bonding electrode includes the light source negative bonding electrode 11 and the detector negative bonding electrode 20; the process method for forming the planarization dielectric layer 21 is a Damascus process. In this embodiment, the planarization dielectric layer 21 preferably uses borophosphosilicate glass. In addition, the lower surface of the planarization dielectric layer 21 needs to be relatively flat in the horizontal direction, so that the lower surfaces of the light source positive bonding electrode 10 and the light source negative bonding electrode 11 can be on the same horizontal line, which is beneficial to the bonding with the substrate 22 in the subsequent process.

[0143] like Fig.10 and Fig.16 As shown, the next step is to perform step S6, invert the above structure, and photolithography and etching through holes on the silicon substrate 100 to form a silicon substrate layer 28.

[0144] It should be noted that the number of through holes is 2, which are respectively located directly above the light source multi-quantum well layer 6 and the detector multi-quantum well layer 15, the through hole is larger at the top and smaller at the bottom, and the cross-sectional shape of the through hole is rectangular or circular, and the specific shape and size can be selected according to actual conditions and are not limited here. In addition, in this step, deep silicon etching technology is used for etching after photolithography to remove the silicon material directly above the multi-quantum well layer.

[0145] like Fig.10 and Fig.17As shown, step S7 is then performed to coat a light-transmitting material higher than the silicon substrate layer 28 on the surface of the structure and in the through hole to form the light-transmitting layer 29 .

[0146] It should be noted that the upper surface of the light-transmitting layer 29 is higher than the silicon substrate layer 28 and is relatively flat, which is conducive to the deposition of the visible light reflecting layer 30 thereon.

[0147] like Fig.10 and Fig.18 As shown, step S8 is then performed to sequentially form the visible light reflecting layer 30 and the contact protection layer 31 on the light-transmitting layer 29 .

[0148] It should be noted that the visible light reflection layer 30 is formed by first depositing a layer of metal Ag on the light transmission layer 29 and then peeling it off to form it; the contact protection layer 31 is formed by spin coating or deposition.

[0149] like Fig.19 As shown, as an example, in step S6, after forming a plurality of the positive bonding electrodes and the negative bonding electrodes, the step of bonding the obtained structure to the substrate 22 through the squirrel substrate bonding metal 23 is also included, and the surface or interior of the substrate 22 contains a circuit unit 25, and the circuit unit 25 is used to process and analyze the output signal of the Micro LED. In this embodiment, it is mainly used to process and analyze the output signals of the Micro LED light source 3 and the Micro LED detector 4.

[0150] In summary, the present invention provides a tactile sensor array based on silicon-based Micro LED and a preparation method thereof, wherein the tactile sensor array includes tactile sensor device units that are regularly distributed, and the tactile sensor device units include two Micro LEDs, one of which is a Micro LED light source and the other is a Micro LED detector; the tactile sensor device unit is used to realize the tactile sensing function, and its distribution density determines the resolution of the tactile sensing. The tactile sensor array based on silicon-based Micro LED of the present invention adopts a silicon-based epitaxial wafer, so that the direct coupling of light is reduced, which is beneficial to reducing the background noise of the sensor; the present invention utilizes MEMS process technology, and the final device is small in size and light in weight, and the production cost can be reduced through mass production, which is beneficial to the application and promotion of the present invention; based on the principle of photoelectric detection, the tactile sensor array of the present invention has the advantages of high resolution and sensitivity, fast response speed and strong anti-electromagnetic interference ability; the size of the tactile sensor array of the present invention can be scaled according to the process capability of the preparation, and through large-scale and high-density integration, a high-resolution tactile sensing function is realized. Therefore, the present invention effectively overcomes the various shortcomings in the prior art and has a high industrial utilization value.

[0151] The above embodiments are merely illustrative of the principles and effects of the present invention, and are not intended to limit the present invention. Anyone familiar with the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by a person of ordinary skill in the art without departing from the spirit and technical concept disclosed by the present invention shall still be covered by the claims of the present invention.

Claims

1. A tactile sensor array based on silicon-based Micro LED, characterized in that: The silicon-based Micro LED tactile sensor array comprises: regularly distributed tactile sensor device units (1); The tactile sensor device unit (1) comprises two Micro LEDs, one of which is used as a Micro LED light source (3) and the other is used as a Micro LED detector (4); The Micro LED light source (3) comprises: A light source active layer, the light source active layer comprising, from bottom to top, a light source P-type GaN layer (5), a light source multi-quantum well layer (6) and a light source N-type GaN layer (7); A light source positive electrode (8), located below the light source P-type GaN layer (5); A light source negative electrode (9), which is in direct contact with the lower side of the light source N-type GaN layer (7) and has a gap with the platform formed by the light source P-type GaN layer (5) and the light source multi-quantum well layer (6); A planarized dielectric layer (21), covering below the light source positive electrode (8) and the light source negative electrode (9); A light source positive bonding electrode (10) located below the light source positive electrode (8), the light source positive bonding electrode (10) comprising two parts, a columnar part penetrating the planarizing dielectric layer (21), and another part covering the surface of the planarizing dielectric layer (21); A light source negative bonding electrode (11) located below the light source negative electrode (9), the light source negative bonding electrode (9) comprising two parts, a columnar part penetrating the planarizing dielectric layer (21), and another part covering the surface of the planarizing dielectric layer (21); A light source non-intentionally doped GaN layer (12) and a light source material buffer layer (13), which are sequentially located above the light source N-type GaN layer (7); The Micro LED detector (4) has the same structure as the Micro LED light source (3), and the Micro LED detector (4) is located on the side of the Micro LED light source (3); The tactile sensor device unit (1) further comprises: a silicon substrate layer (28) located above the light source material buffer layer (13); two through holes are provided on the silicon substrate layer (28), respectively located above the two Micro LED active layers; one of the through holes exposes the Micro LED light source (3), and the other through hole exposes the Micro LED detector (4); part of the light emitted by the Micro LED light source (3) is reflected by the reflective layer (30) onto the Micro LED detector (4); A light-transmitting layer (29), the light-transmitting layer (29) being used to fill the through hole of the silicon substrate layer (28) and cover the upper surface of the silicon substrate layer (28); The visible light reflecting layer (30) and the contact protection layer (31) are sequentially located above the light-transmitting layer (29).

2. The tactile sensor array based on silicon-based Micro LED according to claim 1, characterized in that: The tactile sensor device unit (1) is bonded to a substrate (22) via a substrate bonding metal (23); a circuit unit (25) is contained on the surface or inside of the substrate (22); and the circuit unit (25) is used to process and analyze an output signal of the Micro LED.

3. The tactile sensor array based on silicon-based Micro LED according to claim 1, characterized in that: An isolation groove is provided between the Micro LED light source (3) and the Micro LED detector (4), and isolation metal (33) is provided in the isolation groove.

4. The tactile sensor array based on silicon-based Micro LED according to claim 1, characterized in that: The silicon-based Micro LED tactile sensor array further comprises pulse sensor device units (2); the number of the pulse sensor device units (2) is less than that of the tactile sensor device units (1), and the pulse sensor device units (2) are orderly distributed in the tactile sensor array; the structure of the pulse sensor device unit (2) differs from that of the tactile sensor device unit (1) in that the pulse sensor device unit (2) does not include the visible light reflection layer (30) in the tactile sensor device unit (1).

5. The tactile sensor array based on silicon-based Micro LED according to claim 4, characterized in that: The pulse sensor device unit (2) is bonded to the substrate (22) via a substrate bonding metal (23); the surface or interior of the substrate (22) contains a circuit unit (25); the circuit unit (25) is used to process and analyze the output signal of the Micro LED.

6. The silicon-based Micro LED tactile sensor array according to claim 1, characterized in that: The maximum width of the light source multi-quantum well layer (6) is less than 100 μm.

7. The tactile sensor array based on silicon-based Micro LED according to claim 1, characterized in that: The through hole arranged on the silicon substrate layer (28) is larger at the top and smaller at the bottom, and the cross-sectional shape of the through hole is rectangular or circular.

8. The silicon-based Micro LED tactile sensor array according to claim 1, characterized in that: The material of the visible light reflection layer (30) is metal Ag, and the material of the contact protection layer (31) is resin.

9. A method for preparing a tactile sensor array based on silicon-based Micro LED according to any one of claims 1 to 8, characterized in that: The preparation method comprises: S1: providing a silicon-based gallium nitride LED epitaxial wafer, wherein the silicon-based gallium nitride LED epitaxial wafer comprises, from bottom to top, a silicon substrate (100), a material buffer layer (200), an unintentionally doped GaN material layer (300), an N-type GaN material layer (400), a multi-quantum well material layer (500), and a P-type GaN material layer (600); S2: performing photolithography and etching on the front side of the silicon-based gallium nitride LED epitaxial wafer until the silicon substrate (100) is stopped, thereby forming isolation grooves between different regions; and then performing photolithography and etching on the front side of the silicon-based gallium nitride LED epitaxial wafer until the N-type GaN layer (400) is stopped, thereby forming active layers of different Micro LEDs together with the N-type GaN layer (400); S3: forming a positive electrode of the Micro LED on the front side of the silicon-based gallium nitride LED epitaxial wafer; S4: forming a negative electrode of the Micro LED on the front side of the silicon-based gallium nitride LED epitaxial wafer; S5: forming the planarized dielectric layer (21) on the front side of the silicon-based gallium nitride LED epitaxial wafer, opening holes to form columnar portions of a positive bonding electrode and a negative bonding electrode, and then forming a complete positive bonding electrode and a negative bonding electrode on the surface of the planarized dielectric layer (21); S6: inverting the above structure, photolithography and etching the through hole on the silicon substrate (100), to form a silicon substrate layer (28); S7: coating a light-transmitting material higher than the silicon substrate layer (28) on the surface of the structure and in the through hole to form the light-transmitting layer (29); S8: forming the visible light reflecting layer (30) and the contact protection layer in sequence above the light-transmitting layer (29).

10. The method for preparing a tactile sensor array based on silicon-based Micro LED according to claim 9, characterized in that: In step S6, after forming the positive bonding electrode and the negative bonding electrode, the method further includes bonding the obtained structure to the substrate (22) through a substrate bonding metal (23), wherein the surface or interior of the substrate (22) contains a circuit unit (25), and the circuit unit (25) is used to process and analyze the output signal of the Micro LED.

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