Salient point electrode and preparation method and application thereof

Abstract

The invention belongs to the field of neuroscience and micro-nano machining, and particularly relates to a bump electrode and a preparation method and application thereof. The salient point electrode comprises a flexible substrate, wherein one surface of the flexible substrate is provided with a salient point structure array; the flexible layer is arranged on the surface, with the convex point structure array, of the flexible substrate; the detection electrode array is located on the surface of the flexible layer, each detection electrode comprises a recording site, a connecting line and a bonding pad, one end of each connecting line is connected with the corresponding recording site, the other end of each connecting line is connected with the corresponding bonding pad, each recording site corresponds to one salient point structure, and the other end of each connecting line is connected with the corresponding bonding pad. The recording site covers the upper part and the side surface of the salient point structure; and the packaging layer covers the detection electrode array except for the recording sites. According to the method, the flexible substrate is modified and etched firstly, preparation of other templates is avoided, the preparation method is simple and rapid, and the preparation time is shortened.

Description

Technical Field

[0001] The invention belongs to the field of neuroscience and micro-nano processing, and specifically relates to a convex electrode and a preparation method and application thereof. Background Art

[0002] As a cutting-edge emerging technology that deeply integrates life sciences and information technology, brain-computer interface has broad application value in biomedicine, gaming entertainment, education and other fields. Neural electrodes are an important component of brain-computer interface. They can judge the function and status of nerves, muscles and organs by monitoring electrophysiological signals, which is crucial for understanding the causes of diseases and developing precise treatments. Increasing the contact area between neural electrodes and the neural layer in the brain is conducive to obtaining low-noise and high-quality neural signals. However, the electrodes currently widely used have packaging layer steps, which are not conducive to direct contact with the neural layer.

[0003] CN108553755A discloses a flexible three-dimensional neural electrode and a preparation method thereof, which increases the contact area between the detection site and the brain tissue and obtains a more sensitive and stable neural electrophysiological signal, but the preparation method is relatively complicated. The flexible substrate needs to first prepare a PDMS template with a groove array and a PI template with a through-hole array, then set the PI template on the surface of the PDMS template with the groove array, and finally drip a flexible substrate precursor on the surface of the PI template, and then peel off the cured flexible substrate precursor to obtain it.

[0004] Therefore, the art hopes to develop an electrode that can improve the quality of neural signal detection and has a simple manufacturing method. Summary of the invention

[0005] The purpose of the present invention is to provide a convex electrode and a preparation method and application thereof.

[0006] A first aspect of the present invention provides a bump electrode, the bump electrode comprising:

[0007] A flexible substrate, wherein a surface of the flexible substrate has a convex structure array;

[0008] A flexible layer, wherein the flexible layer is disposed on the surface of the flexible substrate having the convex point structure array;

[0009] A detection electrode array, the detection electrode array is located on the surface of the flexible layer, each detection electrode comprises a recording site, a connection line and a pad, one end of the connection line is connected to the recording site, and the other end of the connection line is connected to the pad, each of the recording sites corresponds to a convex point structure, and the recording sites cover the top and side of the convex point structure;

[0010] A packaging layer covers the detection electrode array except the recording sites.

[0011] In one or more embodiments, the bump electrode has one or more of the following features:

[0012] The material of the flexible substrate is selected from one or more of polyimide, polydimethylsiloxane and platinum-catalyzed silicone rubber;

[0013] The material of the flexible layer is selected from one or more of polyimide, polydimethylsiloxane and platinum-catalyzed silicone rubber;

[0014] The material of the detection electrode array is selected from one or more of gold, platinum, iridium and titanium;

[0015] The material of the encapsulation layer is selected from one or more of photoresist SU-8, polyparaxylene and polyimide.

[0016] In one or more embodiments, the bump electrode has one or more of the following features:

[0017] The thickness of the flexible substrate is 2-50 μm;

[0018] The height of the bump structure is 2-10 μm;

[0019] The thickness of the flexible layer is 1-5 μm;

[0020] The thickness of the detection electrode array is 50-500nm;

[0021] The thickness of the encapsulation layer is 1-20 μm.

[0022] In one or more embodiments, the flexible layer controls the slope of the recording site to be 110°-170°, where the slope of the recording site is the angle between the top surface and the side surface of the recording site.

[0023] In one or more embodiments, the detection electrode array is connected to the flexible layer via an adhesive layer.

[0024] In one or more embodiments, the material of the bonding layer is selected from one or more of titanium, chromium and titanium-tungsten alloy; and / or the thickness of the bonding layer is 10-100 nm.

[0025] The second aspect of the present invention provides a method for preparing the bump electrode according to the first aspect of the present invention, the method comprising the steps of:

[0026] (1) providing a carrier having a metal sacrificial layer on the surface;

[0027] (2) preparing a flexible substrate on the surface of the metal sacrificial layer;

[0028] (3) preparing a first photoresist layer on the surface of the flexible substrate, and patterning the first photoresist layer into a first photoresist bump array;

[0029] (4) etching the sample obtained in step (3) to remove the first photoresist bump array, thereby obtaining a flexible substrate having a bump structure array;

[0030] (5) preparing a flexible layer on the surface of the flexible substrate;

[0031] (6) preparing a detection electrode array on the surface of the flexible layer, wherein the recording sites are located above and on the sides of the convex structure, and the connecting wires and pads are located above the non-convex structure;

[0032] (7) A packaging layer is prepared on the surface of the sample prepared in step (6), wherein the packaging layer does not cover the recording site.

[0033] In one or more embodiments, in step (6), before preparing the detection electrode array, an adhesive layer is first evaporated.

[0034] In one or more embodiments, the method further comprises step (8): removing the metal sacrificial layer and the carrier.

[0035] In one or more embodiments, the method has one or more of the following features:

[0036] The carrier is selected from glass and / or silicon wafer;

[0037] The material of the metal sacrificial layer is selected from one or more of aluminum, chromium, titanium and iron;

[0038] The thickness of the metal sacrificial layer is 10-100 nm.

[0039] The process for preparing the bump electrode of the present invention is simple, fast and efficient. The method of the present invention first modifies and etches the bottom flexible substrate, avoids the preparation of other templates, simplifies the preparation process, reduces the preparation time, and facilitates the mass production and optimized design of neural electrodes.

[0040] Compared with traditional electrodes with packaging layer steps, the bump electrode of the present invention improves the step slope and has a bump structure that is more suitable for attachment to the cerebral cortex, thereby increasing the contact area between the bump electrode of the present invention and the cerebral cortex, helping to improve the quality of neuroelectrophysiological signal detection and better meeting the needs of acute experiments and long-term implantation experiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 It is a schematic cross-sectional view of the bump electrode of the present invention.

[0042] Figure 2is a SEM image of recording sites of two bump electrodes with different diameters in one or more embodiments of the present invention.

[0043] Figure 3 It is a flow chart of the production of bump electrodes in one or more embodiments of the present invention.

[0044] Figure 4 is a schematic diagram of a probe-shaped bump electrode in one or more embodiments of the present invention.

[0045] Figure 5 Schematic diagram of a ring-shaped bump electrode in one or more embodiments of the present invention. DETAILED DESCRIPTION

[0046] In order to enable those skilled in the art to understand the characteristics and effects of the present invention, the following is a general description and definition of the terms and expressions mentioned in the specification and claims. Unless otherwise specified, all technical and scientific terms used in the text are the common meanings understood by those skilled in the art for the present invention. In the event of a conflict, the definition in this specification shall prevail.

[0047] The theories or mechanisms described and disclosed herein, whether correct or incorrect, should not limit the scope of the present invention in any way, that is, the present invention can be implemented without being limited by any specific theory or mechanism.

[0048] Herein, “comprising”, “including”, “containing” and similar terms encompass the meanings of “consisting essentially of” and “consisting of”. For example, when “A comprises B and C” is disclosed herein, “A consists essentially of B and C” and “A consists of B and C” should be deemed to be disclosed herein.

[0049] In this article, all features such as values, quantities, contents and concentrations defined in the form of numerical ranges or percentage ranges are only for brevity and convenience. Accordingly, the description of numerical ranges or percentage ranges should be considered to have included and specifically disclosed all possible secondary ranges and individual values ​​within the range (including integers and fractions).

[0050] In this document, unless otherwise specified, percentage refers to mass percentage and ratio refers to mass ratio.

[0051] Herein, when describing embodiments or examples, it should be understood that they are not used to limit the present invention to these embodiments or examples. On the contrary, all substitutes, improvements and equivalents of the methods and materials described in the present invention can be included in the scope limited by the claims.

[0052] In this document, in order to make the description concise, not all possible combinations of various technical features in various embodiments or examples are described. Therefore, as long as there is no contradiction in the combination of these technical features, the various technical features in various embodiments or examples can be combined arbitrarily, and all possible combinations should be considered to be within the scope of this specification.

[0053] Traditional electrodes are not conducive to direct contact with nerves due to the steps of the packaging layer. The present invention finds that by first etching the surface of the flexible substrate to form a convex structure array with a certain height, and then preparing a flexible layer on the side of the flexible substrate surface with the convex structure array to reduce the step slope, and then preparing a detection electrode array on the surface of the flexible layer, and the recording sites of the detection electrode array cover the top and side of the convex structure, the electrode can be easily and quickly made into a convex shape that is more suitable for attaching to the cerebral cortex, which helps to improve the quality of signal detection and meet the needs of acute experiments and long-term implantation experiments.

[0054] Therefore, the present invention provides a flexible substrate. The surface of the flexible substrate of the present invention has a convex structure array.

[0055] The flexible substrate needs to meet the requirements of biocompatibility and have good insulation and flexibility. The material of the flexible substrate is not specifically limited in this article. Exemplary flexible substrate materials include, but are not limited to, one or more of polyimide (PI), polydimethylsiloxane (PDMS) and platinum-catalyzed silicone rubber, preferably polyimide.

[0056] The thickness of the flexible substrate may be 2-50 μm, for example, 2 μm, 5 μm, 10 μm, 15 μm, 20 μm, 30 μm, 40 μm.

[0057] The height of the bump structure may be 2-10 μm, for example, 2 μm, 3 μm, 5 μm, or 8 μm.

[0058] The area of ​​the surface of the convex structure parallel to the horizontal plane is 200-500 μm 2 , for example 200 μm 2 , 250μm 2 、300μm 2 、350μm 2 , 400μm 2 、450μm 2 .

[0059] The present invention does not impose any particular restrictions on the shape of the bump structure, as long as it is suitable for attaching to the cerebral cortex. Exemplary bump structures may be in the shape of a circle, a square, a trapezoid, or the like.

[0060] A flexible layer is also provided on the surface of the flexible substrate having an array of convex structures. The material of the flexible layer can be selected from one or more of polyimide, polydimethylsiloxane (PDMS) and platinum-catalyzed silicone rubber. The material of the flexible layer is preferably the same as that of the flexible substrate. The thickness of the flexible layer can be 1-5 μm, for example, 1 μm, 2 μm, 3 μm, 4 μm, 5 μm. The flexible layer can control the slope of the recording site arranged above the convex structure to 110°-170°, for example, 110°, 120°, 130°, 140°, 150°, 160°, 170°, and the slope of the recording site is the angle between the top surface and the side surface of the recording site. Controlling the slope of the recording site within the aforementioned range is conducive to the contact between the recording site and the nerve, and helps to improve the quality of signal detection. In the present invention, the slope of the recording site can be observed using SEM.

[0061] The present invention also provides the use of the flexible substrate of the present invention in preparing an electrode. Preferably, the electrode is a neural electrode.

[0062] The present invention provides a method for preparing a flexible substrate, the method comprising the steps of:

[0063] (A) providing a carrier having a metal sacrificial layer on the surface;

[0064] (B) preparing a flexible substrate on the surface of the metal sacrificial layer;

[0065] (C) preparing a first photoresist layer on the surface of the flexible substrate, and patterning the first photoresist layer into a first photoresist bump array;

[0066] (D) etching the sample obtained in step (C), removing the first photoresist bump array, and obtaining a flexible substrate with a bump structure array.

[0067] The carrier may be any carrier known in the art, preferably a silicon wafer or glass.

[0068] The metal sacrificial layer can be a metal commonly used in the art that is easy to remove, for example, can be selected from one or more of aluminum, chromium, titanium and iron, preferably aluminum. The thickness of the metal sacrificial layer can be selected from 10-100nm, for example, 10nm, 20nm, 30nm, 40nm, 50nm, 60nm, 70nm, 80nm.

[0069] In step (B), the flexible substrate can be obtained by heating and curing a heat-curable resin. In some embodiments, step (B) includes: curing a solution containing a heat-curable resin on the surface of the metal sacrificial layer to form a flexible substrate.

[0070] Preferably, the heat-curable resin is polyimide. The solvent of the solution can be a commonly used solvent in the art, as long as it has no adverse effect on the heat curing reaction. The solution containing the heat-curable resin can be a mixed solution of polyimide and pyrrolidone. In the mixed solution of polyimide and pyrrolidone, the mass fraction of polyimide is 10-30%, for example, 10%, 15%, 20%, 25% or 30%.

[0071] Preferably, the solution containing the heat curable resin is coated on the surface of the metal sacrificial layer by spin coating. The rotation speed of the spin coating can be 500-3000 rpm, such as 1000 rpm, 1500 rpm, 2000 rpm, 2500 rpm or 3000 rpm.

[0072] Preferably, the curing temperature is 120-350°C, for example 160°C, 170°C, 180°C, 190°C, 200°C, 220°C or 250°C.

[0073] Preferably, the curing time is 30-180 min, for example, 30 min, 45 min, 60 min, 75 min, 90 min, 120 min, 150 min, 180 min.

[0074] Step (C) comprises: spin coating a first photoresist on the surface of the flexible substrate layer, pre-baking, exposing, and developing to form a first photoresist layer having a bump array. Preferably, the first photoresist is selected from one or both of AZ9620 and AZ4620. The position, shape, and size of the bump array obtained by patterning the first photoresist layer are the same as the bump structure array of the flexible substrate to be prepared.

[0075] Preferably, the rotation speed of the spin coating first photoresist is 1000-4500rpm, such as 1000rpm, 1500rpm, 2000rpm, 2500rpm or 3000rpm. Preferably, the temperature of the pre-bake is 90-130°C, such as 90°C, 100°C, 110°C, 120°C or 130°C. Preferably, the time of the pre-bake is 60-300s, such as 60s, 120s, 180s, 240s or 300s. Preferably, the exposure is ultraviolet exposure. Preferably, the exposure time is 8-100s, such as 8s, 20s, 40s, 60s or 80s. Preferably, the developing time is 30-1000s, such as 100s, 300s, 500s, 700s, 900s or 1000s.

[0076] In step (D), the surface of the sample obtained in step (C) can be etched by conventional processes in the art. Preferably, step (D) includes: etching the sample obtained in step (C) by reactive ion etching.

[0077] In some embodiments, the gas used for reactive ion etching is oxygen. Preferably, the etching pressure is 10-40 Pa, such as 10 Pa, 20 Pa, 30 Pa or 40 Pa. Preferably, the etching time is 30-90 min, such as 30 min, 45 min, 60 min, 75 min or 90 min. Preferably, the etching power is 50-120 W, such as 60 W, 80 W, 100 W, 120 W.

[0078] In step (D), the first photoresist bump array on the surface of the etched flexible substrate layer can be removed by conventional methods in the art. An exemplary method includes soaking the etched sample in acetone to remove the first photoresist bump array.

[0079] The method for preparing a flexible substrate of the present invention further comprises step (E): preparing a flexible layer on the surface of the flexible substrate having a convex structure array obtained in step (D). The flexible layer can be prepared by conventional methods in the art, for example, a solution containing a heat-curable resin can be cured on the surface of the flexible substrate having a convex structure array obtained in step (D) to form a flexible layer. The definition of the flexible layer is as described in any embodiment of the present invention.

[0080] The bump electrode prepared by using the flexible substrate of the present invention has a convex shape which is more suitable for attaching to the cerebral cortex. Therefore, the present invention also provides a bump electrode.

[0081] The bump electrode of the present invention comprises:

[0082] A flexible substrate, wherein a surface of the flexible substrate has a convex structure array;

[0083] A flexible layer, the flexible layer is arranged on the surface of the flexible substrate having the convex point structure array, so as to improve the step slope;

[0084] A detection electrode array, the detection electrode array is located on the surface of the flexible substrate, each detection electrode comprises a recording site, a connection line and a pad, one end of the connection line is connected to the recording site, and the other end of the connection line is connected to the pad, each of the recording sites corresponds to a convex structure, and the recording sites cover the top and side of the convex structure;

[0085] A packaging layer covers the detection electrode array except the recording sites.

[0086] like Figure 1As shown, the bump electrode of the present invention includes a flexible substrate 10 having a bump structure array on its surface. A flexible layer 20 is provided on the surface of the flexible substrate 10 having the bump structure array, and the flexible layer 20 is used to improve the step slope of the bump structure and further improve the slope of the recording site. The detection electrode array is provided on the surface of the flexible layer 20, and each detection electrode includes a recording site 310, a connecting line and a pad. Each recording site 310 corresponds to a bump structure 110. The recording site 310 is used to contact the surface of the brain to obtain neural electrical signals in the brain, and the pad is used to connect to an external circuit to transmit the electrochemical signal obtained by the recording site 310 to the external circuit. The bump electrode of the present invention also includes a packaging layer 40 that covers the detection electrode array except the bump structure array. As shown Figure 2 As shown, the bump electrode with a flexible layer structure of the present invention can indeed improve the steepness of the steps after etching, and can effectively improve the gentleness of the step slope at the recording site.

[0087] When performing brain surface neural signal detection, due to the complex curved structure of the brain surface, the rigid neural electrode cannot form a close contact interface with the brain surface, resulting in a large attenuation of the detected signal and a small amplitude; in addition, the signal noise obtained at the signal detection site of the planar structure is also large. The present invention sets the recording site 310 above and on the side of the convex structure 110. Since the flexible substrate 10 and the flexible layer 20 are easy to bend, they are easy to form a good conformal contact with the brain surface, which increases the contact area between the recording site 310 and the brain, and can reduce the attenuation of the detection signal, so as to obtain a larger signal amplitude. Setting the recording site 310 above and on the side of the convex structure 110 can make the recording site 310 have a three-dimensional structure, improve the step slope of the convex electrode, further increase the contact area between the recording site 310 and the brain, reduce the noise level of the detection signal, and obtain a more sensitive and stable neural electrophysiological signal.

[0088] Conventional electrode materials in the art may be used to prepare the detection electrode array. For example, the material of the detection electrode array is selected from one or more of gold, platinum, iridium and titanium, preferably gold.

[0089] Conventional insulating materials in the art may be used to prepare the encapsulation layer. For example, the material of the encapsulation layer may be selected from one or more of photoresist (such as SU-8), parylene, and polyimide (PI).

[0090] The thickness of the detection electrode array may be 50-500 nm, for example, 50 nm, 100 nm, 150 nm, 200 nm, 250 nm, 300 nm, 400 nm.

[0091] The encapsulation layer may have a thickness of 1-20 μm, for example, 2 nm, 5 nm, 8 nm, 10 nm, 15 nm, or 18 nm.

[0092] Preferably, the detection electrode array is connected to the flexible layer through an adhesive layer, and the adhesive layer can enhance the adhesion between the detection electrode array and the flexible layer. Conventional metal materials in the art can be used as the adhesive layer. Exemplary materials of the adhesive layer can be selected from one or more of titanium, chromium and titanium-tungsten alloy, preferably titanium. The thickness of the adhesive layer can be 10-100nm, for example 10nm, 20nm, 30nm, 40nm, 50nm, 60nm, 70nm, 80nm, 90nm, 100nm.

[0093] In some embodiments, the bump electrode is a neural electrode.

[0094] The present invention does not impose any particular restrictions on the shape of the bump electrode, as long as the bump electrode can be used as a neural electrode. An exemplary bump electrode shape may be Figure 4 The probe-like or Figure 5 The piercing shape shown.

[0095] It should be noted that Figure 1 The figure only shows several detection electrodes and the sizes of the detection electrodes by way of example, which is not a limitation of the present invention. In practical applications, the number and size of the detection electrodes can be selected as required.

[0096] The present invention also provides a method for preparing the bump electrode of the present invention, the method comprising the steps of:

[0097] (a) providing a flexible substrate having a convex structure array on its surface and a flexible layer disposed on the surface having the convex structure array;

[0098] (b) preparing a detection electrode array on the surface of the flexible layer, wherein the recording sites are located above and on the sides of the convex structure, and the connecting wires and pads are located above the non-convex structure;

[0099] (c) preparing a packaging layer on the surface of the sample prepared in step (b), wherein the packaging layer does not cover the recording site.

[0100] The method for preparing the bump electrode of the present invention further comprises step (d): removing the metal sacrificial layer and the carrier.

[0101] In step (a), the flexible substrate having a convex dot structure array on its surface and a flexible layer disposed on the surface having the convex dot array structure can be prepared by the method described herein or any existing method.

[0102] In step (b), the detection electrode array can be prepared by conventional methods in the art, for example, by vapor-depositing the detection electrode array on a flexible substrate through a mask. In some embodiments, step (b) includes: spin coating photoresist on the surface of the flexible layer on the flexible substrate, pre-baking, ultraviolet exposure using a first mask, development, and vapor-depositing the detection electrode array. Before vapor deposition, a photoresist layer with a pattern of recording sites, connecting lines and pad arrays is formed on the surface of the flexible layer on the flexible substrate using a first mask, wherein the recording site pattern is located on the surface of the convex structure. Preferably, before vapor-depositing the detection electrode array, an adhesive layer is first vapor-deposited. Preferably, after vapor-depositing the detection electrode array, the photoresist layer is removed using conventional methods in the art, such as immersion in acetone.

[0103] Preferably, the photoresist is selected from one or both of photoresists AZ9620 and AZ4620. Preferably, the rotation speed of the spin-coated photoresist is 1000-5000rpm, such as 1000rpm, 2000rpm, 3000rpm, 4000rpm, 4500rpm or 5000rpm. Preferably, the temperature of the pre-bake is 90-130°C, such as 90°C, 100°C, 110°C, 120°C, or 130°C. Preferably, the time of the pre-bake is 60-300s, such as 60s, 120s, 180s, 240s or 300s. Preferably, the UV exposure time is 8-100s, such as 8s, 20s, 40s, 60s or 80s. Preferably, the development time is 30-1000 s, for example 100 s, 300 s, 500 s, 700 s, 900 s or 1000 s.

[0104] In step (c), the encapsulation layer can be prepared by the method described herein or any existing method. For example, step (c) includes the steps of: preparing a flexible polymer layer on the surface of the sample prepared in step (b); preparing a second photoresist layer on the surface of the flexible polymer layer, and patterning the second photoresist layer so that there is no second photoresist layer directly above the bump structure array; etching the flexible polymer layer and the second photoresist layer to obtain a bump electrode exposing the recording site. The flexible polymer layer can be prepared by conventional methods in the art, for example, by heating and curing a solution containing a heat-curable resin, and the heating and curing can be carried out under conventional conditions in the existing methods, or under the heating and curing conditions defined in this article. The material of the flexible polymer layer can be a conventional material in the field of flexible electrodes, for example, the material of the flexible polymer layer can be selected from one or more of polyimide, polydimethylsiloxane and platinum-catalyzed silicone rubber; preferably the same as the material of the flexible substrate. The second photoresist layer can be patterned by the method described herein or any existing method. The flexible polymer layer and the second photoresist layer can be etched by the method described herein or any existing method.

[0105] In some embodiments, the method of preparing a bump electrode of the present invention comprises the steps of:

[0106] (1) providing a carrier having a metal sacrificial layer on the surface;

[0107] (2) preparing a flexible substrate on the surface of the metal sacrificial layer;

[0108] (3) preparing a first photoresist layer on the surface of the flexible substrate, and patterning the first photoresist layer into a first photoresist bump array;

[0109] (4) etching the sample obtained in step (3) to remove the first photoresist bump array, thereby obtaining a flexible substrate having a bump structure array;

[0110] (5) preparing a flexible layer on the surface of the flexible substrate;

[0111] (6) preparing a detection electrode array on the surface of the flexible layer, wherein the recording sites are located above and on the sides of the convex structure, and the connecting wires and pads are located above the non-convex structure;

[0112] (7) A packaging layer is prepared on the surface of the sample prepared in step (6), wherein the packaging layer does not cover the recording site.

[0113] Preferably, in step (6), a bonding layer is first prepared on the surface of the flexible substrate, and then the detection electrode array is prepared. The material and thickness of the bonding layer are as described in any embodiment of the present invention. The bonding layer can be prepared by conventional methods in the art, such as evaporation.

[0114] Preferably, the method further comprises step (8): removing the metal sacrificial layer and the carrier. The metal sacrificial layer can be removed by conventional methods in the art, such as electrochemical etching methods and acid (such as dilute hydrochloric acid) etching methods.

[0115] Preferably, the method for preparing a bump electrode of the present invention comprises the steps of:

[0116] (1) Thermally evaporate or sputter a layer of metal on a silicon wafer or glass as a metal sacrificial layer;

[0117] (2) preparing a flexible substrate on the metal sacrificial layer;

[0118] (3) spin coating a first photoresist on the surface of the flexible substrate, and patterning the first photoresist layer using a photolithography process to obtain a first photoresist bump array;

[0119] (4) etching the sample obtained in step (3) to form a bump structure array on the flexible substrate, removing the first photoresist bump array, and obtaining a flexible substrate having a bump structure array;

[0120] (5) preparing a flexible layer on the surface of the flexible base layer;

[0121] (6) spin coating a second photoresist on the flexible layer, patterning the second photoresist layer using a photolithography process to obtain a mask, and then evaporating a detection electrode array on the flexible layer, with the recording sites located above and on the sides of the bump structure;

[0122] (7) sequentially spin-coating an insulating material layer and a third photoresist on a surface of the detection electrode array away from the flexible substrate, patterning the third photoresist layer using a photolithography process; and etching the insulating material layer to expose the recording site;

[0123] (8) The recording site is released by electrochemically etching or dilute acid etching the metal sacrificial layer, followed by soaking, rinsing and drying with deionized water.

[0124] The present invention will be further described below in conjunction with specific examples. It should be understood that these examples are only used to illustrate the present invention and are not intended to limit the scope of the present invention. The experimental methods in the following examples without specifying specific conditions are usually based on conventional conditions or the conditions recommended by the manufacturer. Unless otherwise stated, percentages and parts are calculated by weight.

[0125] Example 1

[0126] like Figure 3 , Figure 4 As shown, this embodiment provides a method for simply making a probe-shaped bump electrode, and the specific steps are as follows:

[0127] A 100-micron-thick aluminum layer is deposited by sputtering or thermal evaporation on a 500-micron-thick silicon wafer as a sacrificial layer.

[0128] A mixture of polyimide PI and pyrrolidone was spin-coated on the surface of the sacrificial layer and heated to form a PI film. The mass fraction of PI in the mixture of PI and pyrrolidone was 20%. The rotation speed of spin-coating the mixture of PI and pyrrolidone was 1500 rpm, the heating temperature was 200°C, the heating time was 120 min, and a PI film with a thickness of 7 μm was obtained.

[0129] Figure 3 In step 1, the photoresist AZ9620 is spin-coated on the surface of the PI film, and a photoresist layer with a dot array is formed after pre-baking, exposure, and development, and the diameter of each circle is 20 μm. The rotation speed of the spin-coating photoresist is 1500 rpm, the pre-baking temperature is 110° C., the pre-baking time is 180 s, the UV exposure time is 40 s, and the development time is 400 s.

[0130] Figure 3In step 2, a reactive ion etching device is used to etch the surface of the sample obtained above to form a convex structure array on the PI surface. The gas used for reactive ion etching is oxygen, the pressure of the reactive ion etching device is set to 20Pa, the etching time of the reactive ion etching device is set to 30min, the etching power is 60W, and the height of the convex structure is 3μm.

[0131] Figure 3 In step 3, a second layer of a mixture of PI and pyrrolidone is spin-coated on the surface of the sample, with an initial rotation speed of 500 rpm for 5 seconds; a steady rotation speed of 3000 rpm for 45 seconds; and heating at 200°C in a vacuum drying oven for 60 minutes to obtain a PI film with a thickness of 2 μm to further improve the step slope.

[0132] Figure 3 In step 4, the photoresist AZ9620 is spin-coated on the surface of the PI film with the bump structure, pre-baked, ultraviolet exposed using the first mask, and developed to form a photoresist layer with recording sites, metal wiring and pad array patterns, wherein the recording site pattern is located on the surface of the bump structure; the metal layer is evaporated, and the metal layer includes an adhesive layer and a detection electrode array. After spin-coating the photoresist, the adhesive layer is evaporated first, and then the detection electrode array is evaporated. The evaporation program is set to Ti first and then Au, and the crucible is changed during the evaporation process. The rotation speed of the spin-coated photoresist is 4500rpm, the pre-baking temperature is 110℃, the pre-baking time is 180s, the ultraviolet exposure time is 40s, the development time is 300s, the material of the adhesive layer is titanium, the thickness of the adhesive layer is 10nm, the material of the detection electrode array is gold, the thickness of the detection electrode array is 50nm, and the slope of the recording site is 160°. After evaporating the detection electrode array, the sample is soaked in acetone to remove residual photoresist.

[0133] Figure 3 In step 5, a third layer of polyimide PI and pyrrolidone mixture is spin-coated on the surface of the surface detection electrode array, with an initial rotation speed of 500 rpm, maintained for 5 seconds; a stable rotation speed of 2500 rpm, maintained for 45 seconds; and heated and cured at 200°C for 120 minutes.

[0134] Figure 3 In step 6, the photoresist AZ4620 is spin-coated on the surface of the above PI film, with an initial rotation speed of 500 rpm, maintained for 5 seconds; a stable rotation speed of 2500 rpm, maintained for 45 seconds; pre-baked at 95° C. for 2 minutes; exposed for 8 seconds; and developed for 290 seconds.

[0135] Figure 3 In step 7, a reactive ion etching device is used to etch the exposed PI layer of the sample obtained above, the etching gas used is oxygen, the equipment pressure is 20Pa, the power is 60W, the processing time is 26min, and a 2μm encapsulation layer is obtained.

[0136] Example 2

[0137] like Figure 5 As shown, this embodiment provides a method for simply manufacturing a ring-shaped bump electrode, and the specific manufacturing method is as follows:

[0138] A 100 nm aluminum sacrificial layer was deposited on the surface of a clean silicon wafer, and a mixture of PI and pyrrolidone (PI mass fraction was 18%) was spin-coated on the sacrificial layer. The initial rotation speed was 500 rpm and maintained for 5 s; the steady rotation speed was 2000 rpm and maintained for 60 s; the film was heated at 200°C in a vacuum drying oven for 60 min to obtain a PI film with a thickness of 5 μm.

[0139] The PI film surface was spin-coated with AZ4620 photoresist, with an initial rotation speed of 500 rpm, maintained for 5 seconds; a stable rotation speed of 2500 rpm, maintained for 60 seconds, and a baking plate was heated at 100°C for 3 minutes to obtain a photoresist layer with a film thickness of 8 μm. The film was exposed with a UV exposure machine (MA6) for 40 seconds, developed for 20 minutes, rinsed with deionized water, and dried with a nitrogen gun. The photoresist layer formed a square array structure, in which each rectangle was 15 μm wide and 20 μm long, and the height of the bump structure was 5 μm.

[0140] The above sample was etched by RIE, the gas used for etching was oxygen, the etching power was 60W, the etching time was 20 minutes, the etching pressure was 40Pa, the exposed PI was etched clean to form a square bump structure, and the height of the bump structure was 5μm. The sample was successively rinsed with acetone, isopropanol ultrasound, and deionized water to remove the glue.

[0141] A second layer of a mixture of PI and pyrrolidone was spin-coated on the surface of the sample having the bump structure array side, with an initial rotation speed of 500 rpm, maintained for 5 seconds; a steady rotation speed of 2700 rpm, maintained for 45 seconds; heated at 200°C in a vacuum drying oven for 60 minutes; and a PI film with a thickness of 3 μm was obtained to further improve the step slope.

[0142] The sample was spin-coated with AZ4620 photoresist, with an initial speed of 500 rpm, maintained for 5 seconds, a stable speed of 2500 rpm, maintained for 60 seconds, and a baking plate heated at 100°C for 3 minutes. The first mask was used for exposure for 10 seconds, developed for 215 seconds, rinsed with deionized water, and dried with a nitrogen gun.

[0143] Ti / Au was deposited by electron beam evaporation with a thickness of 10 / 100 nm respectively. The sample after evaporation was immersed in acetone for 20 minutes, and after a large area of ​​glue was removed, it was placed in acetone and isopropanol for ultrasonic treatment in turn, rinsed with deionized water and dried with a nitrogen gun, and the slope of the recording site was 140°.

[0144] Spin-coat the photoresist SU-8 2005 on the surface of the sample, with an initial rotation speed of 500 rpm and maintain for 5 seconds; stabilize the rotation speed at 2000 rpm and maintain for 60 seconds; heat at 95°C for 2 minutes, and the film thickness is about 5 μm. Use the second mask to expose for 150 seconds, develop, fix, and blow dry with high-pressure nitrogen to obtain a 2.5 μm encapsulation layer.

[0145] The recording electrode is released by electrochemically etching or corroding the aluminum sacrificial layer with dilute hydrochloric acid.

Claims

1. A bump electrode, characterized in that: The bump electrode comprises: A flexible substrate, wherein a surface of the flexible substrate has a convex structure array; A flexible layer, wherein the flexible layer is disposed on the surface of the flexible substrate having the convex point structure array; A detection electrode array, the detection electrode array is located on the surface of the flexible layer, each detection electrode comprises a recording site, a connection line and a pad, one end of the connection line is connected to the recording site, and the other end of the connection line is connected to the pad, each of the recording sites corresponds to a convex point structure, and the recording sites cover the top and side of the convex point structure; A packaging layer covers the detection electrode array except the recording sites.

2. The bump electrode according to claim 1, wherein: The bump electrode has one or more of the following features: The material of the flexible substrate is selected from one or more of polyimide, polydimethylsiloxane and platinum-catalyzed silicone rubber; The material of the flexible layer is selected from one or more of polyimide, polydimethylsiloxane and platinum-catalyzed silicone rubber; The material of the detection electrode array is selected from one or more of gold, platinum, iridium and titanium; The material of the encapsulation layer is selected from one or more of photoresist SU-8, polyparaxylene and polyimide.

3. The bump electrode according to claim 1, wherein: The bump electrode has one or more of the following features: The thickness of the flexible substrate is 2-50 μm; The height of the bump structure is 2-10 μm; The thickness of the flexible layer is 1-5 μm; The thickness of the detection electrode array is 50-500nm; The thickness of the encapsulation layer is 1-20 μm.

4. The bump electrode according to claim 1, wherein: The flexible layer controls the slope of the recording site to be 110°-170°, and the slope of the recording site is the angle between the top surface and the side surface of the recording site.

5. The bump electrode according to claim 1, wherein: The detection electrode array is connected to the flexible layer through an adhesive layer.

6. The bump electrode according to claim 5, characterized in that: The material of the bonding layer is selected from one or more of titanium, chromium and titanium-tungsten alloy; and / or the thickness of the bonding layer is 10-100 nm.

7. A method for preparing the bump electrode according to any one of claims 1 to 6, characterized in that: The method comprises the steps of: (1) providing a carrier having a metal sacrificial layer on the surface; (2) preparing a flexible substrate on the surface of the metal sacrificial layer; (3) preparing a first photoresist layer on the surface of the flexible substrate, and patterning the first photoresist layer into a first photoresist bump array; (4) etching the sample obtained in step (3) to remove the first photoresist bump array, thereby obtaining a flexible substrate having a bump structure array; (5) preparing a flexible layer on the surface of the flexible substrate; (6) preparing a detection electrode array on the surface of the flexible layer, wherein the recording sites are located above and on the sides of the convex structure, and the connecting wires and pads are located above the non-convex structure; (7) A packaging layer is prepared on the surface of the sample prepared in step (6), wherein the packaging layer does not cover the recording site.

8. The method according to claim 7, characterized in that In step (6), before preparing the detection electrode array, an adhesive layer is first evaporated.

9. The method according to claim 7, characterized in that The method further comprises step (8): removing the metal sacrificial layer and the carrier.

10. The method according to any one of claims 7 to 9, characterized in that The method has one or more of the following features: The carrier is selected from glass and / or silicon wafer; The material of the metal sacrificial layer is selected from one or more of aluminum, chromium, titanium and iron; The thickness of the metal sacrificial layer is 10-100 nm.

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