Bumped electrodes, their fabrication methods, and applications

Abstract

The present application belongs to the field of neuroscience and micro-nano processing, and particularly relates to a bump electrode and a preparation method and application thereof. The bump electrode comprises a flexible substrate, a surface of the flexible substrate having an array of bump structures; a flexible layer arranged on the surface of the flexible substrate having the array of bump structures; an array of detection electrodes located on the surface of the flexible layer, each detection electrode comprising a recording site, a wire and a pad, one end of the wire being connected with the recording site, the other end of the wire being connected with the pad, each recording site corresponding to one bump structure, and the recording site covering the top and side of the bump structure; and a packaging layer covering the array of detection electrodes except the recording sites. The method of the present application first modifies and etches the flexible substrate, thereby avoiding the preparation of other templates, and the preparation method is simple and fast, and the preparation time is reduced.

Description

Technical Field

[0001] This invention belongs to the field of neuroscience and micro / nano fabrication, specifically relating to a convex electrode, its preparation method, and its application. Background Technology

[0002] As a cutting-edge emerging technology that deeply integrates life sciences and information technology, brain-computer interfaces (BCIs) have broad application value in fields such as biomedicine, gaming, and education. Neural electrodes are a crucial component of BCIs, enabling the monitoring of electrophysiological signals to determine the function and state of nerves, muscles, and organs, which is essential 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 beneficial for obtaining low-noise, high-quality neural signals. However, currently widely used electrodes have encapsulation layer steps, which are not conducive to direct contact with the neural layer.

[0003] CN108553755A discloses a flexible three-dimensional neural electrode and its fabrication method, which increases the contact area between the detection site and brain tissue, resulting in more sensitive and stable neurophysiological signals. However, the fabrication method is relatively complex. The flexible substrate requires first preparing a PDMS template with a groove array and a PI template with a through-hole array. Then, the PI template is placed on the grooved surface of the PDMS template. Finally, a flexible substrate precursor is dropped onto the surface of the PI template, and the resulting flexible substrate precursor is peeled off and cured.

[0004] Therefore, there is a need in the art to develop an electrode that can improve the quality of neural signal detection and is easy to manufacture. Summary of the Invention

[0005] The purpose of this invention is to provide a bump electrode, its preparation method, and its application.

[0006] In a first aspect, the present invention provides a convex electrode, the convex electrode comprising:

[0007] A flexible substrate, wherein one surface of the flexible substrate has an array of protrusion structures;

[0008] A flexible layer is disposed on the surface of a flexible substrate having an array of protrusion structures;

[0009] A detection electrode array is located on the surface of the flexible layer. Each detection electrode includes 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 recording site corresponds to a bump structure, and the recording site covers the top and side of the bump structure.

[0010] An encapsulation layer that covers the detection electrode array except for the recording sites.

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

[0012] 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, parylene, 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 convex 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 50-500 nm;

[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 adhesive layer is selected from one or more of titanium, chromium, and titanium-tungsten alloys; and / or, the thickness of the adhesive layer is 10-100 nm.

[0025] A second aspect of the present invention provides a method for preparing the bump electrode described in the first aspect of the present invention, the method comprising the steps of:

[0026] (1) Provide a carrier with a metal sacrificial layer on its surface;

[0027] (2) A flexible substrate is prepared on the surface of the metal sacrificial layer;

[0028] (3) A first photoresist layer is prepared on the surface of the flexible substrate, and the first photoresist layer is patterned into a first photoresist bump array;

[0029] (4) The sample obtained in etching step (3) is de-etched to remove the first photoresist bump array to obtain a flexible substrate with a bump structure array.

[0030] (5) A flexible layer is prepared on the surface of the flexible substrate;

[0031] (6) A detection electrode array is prepared on the surface of the flexible layer, wherein the recording sites are located above and on the side of the bump structure, and the connecting lines and pads are located above the non-bump structure;

[0032] (7) Prepare an encapsulation layer on the surface of the sample obtained in step (6), wherein the encapsulation layer does not cover the recording site.

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

[0034] In one or more embodiments, the method further includes 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 wafers;

[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 fabricating bump electrodes according to this invention is simple, fast, and efficient. The method of this invention first modifies and etches the underlying flexible substrate, avoiding the preparation of other templates, simplifying the preparation process, reducing preparation time, and facilitating the mass production and optimized design of neural electrodes.

[0040] Compared to traditional electrodes with encapsulation layer steps, the convex electrode of the present invention improves the step slope and has a convex structure that is more suitable for attaching to the cerebral cortex. This increases the contact area between the convex electrode of the present invention and the cerebral cortex, which helps to improve the quality of neurophysiological signal detection and can better meet the needs of acute experiments and long-term implantation experiments. Attached Figure Description

[0041] Figure 1 This is a cross-sectional schematic diagram of the convex electrode of the present invention.

[0042] Figure 2These are SEM images of the recording sites of two protrusion electrodes with different diameters in one or more embodiments of the present invention.

[0043] Figure 3 This is a flowchart illustrating the fabrication process of the convex electrode in one or more embodiments of the present invention.

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

[0045] Figure 5 This is a schematic diagram of an annular protrusion electrode in one or more embodiments of the present invention. Detailed Implementation

[0046] To enable those skilled in the art to understand the features and effects of the present invention, the terms and expressions used in the specification and claims are explained and defined in general below. Unless otherwise specified, all technical and scientific terms used herein have the ordinary meaning understood by those skilled in the art regarding the present invention, and in case of conflict, the definitions in this specification shall prevail.

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

[0048] In this document, the terms “contains,” “includes,” “containing,” and similar terms encompass the meanings of “basically composed of” and “composed of.” For example, when this document discloses “A contains B and C,” “A is basically composed of B and C” and “A is composed of B and C” should be considered as having been disclosed in this document.

[0049] In this document, all features defined by numerical ranges or percentage ranges, such as numerical values, quantities, contents, and concentrations, are for the sake of brevity and convenience only. Accordingly, descriptions of numerical ranges or percentage ranges should be considered as covering and specifically disclosing all possible sub-ranges and individual numerical values ​​(including integers and fractions) within those ranges.

[0050] Unless otherwise specified, percentages refer to mass percentages and proportions refer to mass ratios in this article.

[0051] In this document, when describing embodiments or examples, it should be understood that it is not intended to limit the invention to those embodiments or examples. Rather, all alternatives, modifications, and equivalents of the methods and materials described herein are covered within the scope defined by the claims.

[0052] For the sake of brevity, not all possible combinations of the technical features in each implementation scheme or embodiment are described herein. Therefore, as long as there is no contradiction in the combination of these technical features, the technical features in each implementation scheme or embodiment can be combined arbitrarily, and all possible combinations should be considered within the scope of this specification.

[0053] Traditional electrodes, due to their encapsulation layer steps, are not conducive to direct contact with nerves. This invention discovers that by first etching the surface of a flexible substrate to form an array of raised structures of a certain height, and then preparing a flexible layer on one side of the flexible substrate surface with the raised structure array to reduce the step slope, a detection electrode array can be prepared on the surface of the flexible layer. The recording sites of the detection electrode array cover the top and sides of the raised structures, allowing for a simple and quick way to create electrodes that are more suitable for attachment to the cerebral cortex. This helps improve the quality of signal detection and meets the needs of both acute 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 an array of protrusion structures.

[0055] The flexible substrate must meet biocompatibility requirements and possess good insulation and flexibility. This document does not impose specific limitations on the materials of the flexible substrate. Exemplary flexible substrate materials include, but are not limited to, one or more of polyimide (PI), polydimethylsiloxane (PDMS), and platinum-catalyzed silicone rubber, with polyimide being preferred.

[0056] The thickness of the flexible substrate can 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 convex structure can be 2-10μm, for example, 2μm, 3μm, 5μm, 8μm.

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

[0059] This invention does not impose any special restrictions on the shape of the protrusion structure, as long as it is suitable for attachment to the cerebral cortex. Exemplary protrusion structures can be circular, square, trapezoidal, etc.

[0060] A flexible layer is further disposed 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. Preferably, the material of the flexible layer is 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. This flexible layer can control the slope of the recording site disposed above the convex structure to 110°-170°, for example, 110°, 120°, 130°, 140°, 150°, 160°, 170°, where 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 beneficial for the contact between the recording site and the nerve, and helps to improve the quality of signal detection. In this invention, the slope of the recording site can be observed using SEM.

[0061] This invention also provides the application of the flexible substrate of this invention in the fabrication of electrodes. Preferably, the electrode is a neural electrode.

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

[0063] (A) Provide a carrier with a metal sacrificial layer on its surface;

[0064] (B) A flexible substrate is prepared on the surface of the metal sacrificial layer;

[0065] (C) A first photoresist layer is prepared on the surface of the flexible substrate, and the first photoresist layer is patterned into a first photoresist bump array;

[0066] (D) The sample obtained in etching step (C) is used to remove the first photoresist bump array to obtain a flexible substrate with a bump structure array.

[0067] The carrier can be any carrier 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, such as one or more of aluminum, chromium, titanium and iron, preferably aluminum. The thickness of the metal sacrificial layer can be selected from 10-100 nm, for example 10 nm, 20 nm, 30 nm, 40 nm, 50 nm, 60 nm, 70 nm and 80 nm.

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

[0070] Preferably, the thermosetting resin is polyimide. The solvent of the solution can be a commonly used solvent in the art, as long as it does not adversely affect the thermosetting reaction. The solution containing the thermosetting resin can be a mixture of polyimide and pyrrolidone. In the mixture 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 a thermosetting resin is applied to the surface of the metal sacrificial layer by spin coating. The spin coating speed can be 500-3000 rpm, for example, 1000 rpm, 1500 rpm, 2000 rpm, 2500 rpm or 3000 rpm.

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

[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, or 180 min.

[0074] Step (C) includes: spin-coating a first photoresist onto the surface of a flexible substrate, followed by pre-baking, exposure, and development to form a first photoresist layer with 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 fabricated.

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

[0076] In step (D), the surface of the sample obtained in step (C) can be etched using 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, for example, 10 Pa, 20 Pa, 30 Pa, or 40 Pa. Preferably, the etching time is 30-90 min, for example, 30 min, 45 min, 60 min, 75 min, or 90 min. Preferably, the etching power is 50-120 W, for example, 60 W, 80 W, 100 W, or 120 W.

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

[0079] The method for preparing a flexible substrate according to the present invention further includes step (E): preparing a flexible layer on the surface of the flexible substrate having a bump array obtained in step (D). The flexible layer can be prepared using methods conventional in the art; for example, a solution containing a thermosetting resin can be cured onto the surface of the flexible substrate having a bump array obtained in step (D) to form a flexible layer. The definition of the flexible layer is as described in any embodiment herein.

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

[0081] The convex electrode of the present invention includes:

[0082] A flexible substrate, wherein one surface of the flexible substrate has an array of protrusion structures;

[0083] A flexible layer is disposed on the surface of a flexible substrate having an array of protrusions to improve the slope of the step.

[0084] A detection electrode array is located on the surface of the flexible substrate. Each detection electrode includes 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 recording site corresponds to a bump structure, and the recording site covers the top and side of the bump structure.

[0085] An encapsulation layer that covers the detection electrode array except for the recording sites.

[0086] like Figure 1As shown, the bump electrode of the present invention includes a flexible substrate 10 with a bump structure array on its surface. A flexible layer 20 is disposed on the surface of the flexible substrate 10 with the bump structure array. The flexible layer 20 is used to improve the step slope of the bump structure and further improve the slope of the recording site. A detection electrode array is disposed on the surface of the flexible layer 20. Each detection electrode includes a recording site 310, a connection, 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 acquire neural electrical signals from the brain. The pad is used to connect to an external circuit to transmit the electrochemical signals acquired by the recording site 310 to the external circuit. The bump electrode of the present invention also includes an encapsulation layer 40 covering the detection electrode array other than the bump structure array. Figure 2 As shown, the bump electrode with flexible layer structure of the present invention can indeed improve the steepness of the step after etching and can effectively improve the gentleness of the step slope of the recording site.

[0087] When detecting neural signals on the brain surface, the complex curved structure of the brain surface prevents rigid neural electrodes from forming a tight contact interface, resulting in significant signal attenuation and small amplitude. Furthermore, signal detection sites with planar structures also exhibit higher noise levels. This invention places the recording site 310 above and on the sides of the convex structure 110. Because the flexible base 10 and flexible layer 20 are easily bent, they readily form a good conformal contact with the brain surface, increasing the contact area between the recording site 310 and the brain. This reduces signal attenuation and yields a larger signal amplitude. Placing the recording site 310 above and on the sides of the convex structure 110 gives it a three-dimensional structure, improving the step slope of the convex electrode and further increasing the contact area between the recording site 310 and the brain, reducing the noise level of the detected signal, and resulting in more sensitive and stable neurophysiological signals.

[0088] Electrode materials conventional in the art can 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] The encapsulation layer can be prepared using insulating materials conventional in the art, such as photoresist (e.g., SU-8), parylene, and polyimide (PI).

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

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

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

[0093] In some implementations, the convex electrode is a neural electrode.

[0094] This invention does not impose any particular limitations on the shape of the convex electrode, as long as it can be used as a neural electrode. An exemplary shape of the convex electrode could be... Figure 4 The probe-shaped or Figure 5 The loop shape shown.

[0095] It should be noted that, Figure 1 The illustrations only show a few detection electrodes and their sizes, and are not intended to limit the invention. In practical applications, the number and size of the detection electrodes can be selected as needed.

[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) Provides a flexible substrate of the present invention having a convex dot array on its surface and a flexible layer disposed on the surface having the convex dot array structure;

[0098] (b) A detection electrode array is fabricated on the surface of the flexible layer, with the recording sites located above and on the sides of the bump structure, and the wiring and pads located above the non-bump structure;

[0099] (c) An encapsulation layer is prepared on the surface of the sample obtained in step (b), the encapsulation layer not covering the recording site.

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

[0101] In step (a), the flexible substrate of the present invention 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 fabricated using methods conventional in the art, such as depositing the detection electrode array on a flexible substrate using a mask. In some embodiments, step (b) includes: spin-coating photoresist on the flexible layer surface of the flexible substrate, pre-baking, UV exposure using a first mask, development, and depositing the detection electrode array. Before deposition, a photoresist layer with a pattern of recording sites, interconnects, and pad arrays is formed on the flexible layer surface of the flexible substrate using the first mask, wherein the recording site pattern is located on the surface of the bump structure. Preferably, an adhesive layer is deposited before depositing the detection electrode array. Preferably, after depositing the detection electrode array, the photoresist layer is removed using methods conventional in the art, such as immersion in acetone.

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

[0104] In step (c), the encapsulation layer can be prepared using the methods described herein or any existing methods. For example, step (c) includes the steps of: preparing a flexible polymer layer on the surface of the sample obtained in step (b); preparing a second photoresist layer on the surface of the flexible polymer layer and patterning the second photoresist layer such that there is no second photoresist layer directly above the bump structure array; and etching the flexible polymer layer and the second photoresist layer to obtain bump electrodes exposing recording sites. The flexible polymer layer can be prepared using conventional methods in the art, such as by heating and curing a solution containing a thermosetting resin. The heating and curing can be performed under conventional conditions in existing methods or under the heating and curing conditions defined herein. 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, it is the same as the material of the flexible substrate. The second photoresist layer can be patterned using the methods described herein or any existing methods. The flexible polymer layer and the second photoresist layer can be etched using the methods described herein or any existing methods.

[0105] In some embodiments, the method for preparing a bump electrode according to the present invention includes the steps of:

[0106] (1) Provide a carrier with a metal sacrificial layer on its surface;

[0107] (2) A flexible substrate is prepared on the surface of the metal sacrificial layer;

[0108] (3) A first photoresist layer is prepared on the surface of the flexible substrate, and the first photoresist layer is patterned into a first photoresist bump array;

[0109] (4) The sample obtained in etching step (3) is de-etched to remove the first photoresist bump array to obtain a flexible substrate with a bump structure array.

[0110] (5) A flexible layer is prepared on the surface of the flexible substrate;

[0111] (6) A detection electrode array is prepared on the surface of the flexible layer, wherein the recording sites are located above and on the side of the bump structure, and the connecting lines and pads are located above the non-bump structure;

[0112] (7) Prepare an encapsulation layer on the surface of the sample obtained in step (6), wherein the encapsulation layer does not cover the recording site.

[0113] Preferably, in step (6), an adhesive 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 adhesive layer are as described in any embodiment herein. The adhesive layer can be prepared using conventional methods in the art, such as vapor deposition.

[0114] Preferably, the method further includes step (8): removing the metal sacrificial layer and the support. The metal sacrificial layer can be removed using methods conventional in the art, such as electrochemical etching or acid (e.g., dilute hydrochloric acid) etching.

[0115] Preferably, the method for preparing a bump electrode according to the present invention includes the following steps:

[0116] (1) A layer of metal is thermally evaporated or sputtered onto a silicon wafer or glass as a metal sacrificial layer;

[0117] (2) A flexible substrate is prepared on the metal sacrificial layer;

[0118] (3) Spin-coating the first photoresist onto 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) The sample obtained in etching step (3) forms a bump structure array on the flexible substrate, and the first photoresist bump array is removed to obtain a flexible substrate with a bump structure array.

[0120] (5) A flexible layer is prepared on the surface of the flexible substrate layer;

[0121] (6) Spin-coat the second photoresist onto the flexible layer, use photolithography to pattern the second photoresist layer to obtain a mask, and then deposit the detection electrode array on the flexible layer. The recording sites are located above and on the side of the bump structure.

[0122] (7) An insulating material layer and a third photoresist are sequentially spin-coated on the surface of the detection electrode array away from the flexible substrate, and the third photoresist layer is patterned using a photolithography process; the insulating material layer is etched to expose the recording sites;

[0123] (8) The metal sacrificial layer is released by electrochemical corrosion or dilute acid corrosion, followed by soaking, rinsing and drying with deionized water.

[0124] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Experimental methods in the following embodiments, unless otherwise specified, are generally performed under conventional conditions or as recommended by the manufacturer. Percentages and parts are by weight unless otherwise stated.

[0125] Example 1

[0126] like Figure 3 , Figure 4 As shown in the figure, this embodiment provides a simple method for fabricating a probe-shaped bump electrode. The specific steps are as follows:

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

[0128] A mixture of polyimide (PI) and pyrrolidone was spin-coated onto the surface of the sacrificial layer and then heated to cure, forming a PI film. The mass fraction of PI in the PI-pyrrolidone mixture was 20%. The spin-coating speed of the PI-pyrrolidone mixture was 1500 rpm, the heating temperature was 200℃, and the heating time was 120 min, resulting in a PI film with a thickness of 7 μm.

[0129] Figure 3 In step 1, AZ9620 photoresist is spin-coated onto the PI film surface. After pre-baking, exposure, and development, a photoresist layer with a dot array is formed, with each circle having a diameter of 20 μm. The spin-coating speed is 1500 rpm, the pre-baking temperature is 110℃, 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, the surface of the sample obtained above is etched using a reactive ion etching device to form a bump 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 20 Pa, the etching time is set to 30 min, the etching power is 60 W, and the height of the bump structure is 3 μm.

[0131] Figure 3 In step 3, a second layer of PI and pyrrolidone mixture is spin-coated onto the surface of the sample. The initial spin speed is 500 rpm, maintained for 5 s; the stable spin speed is 3000 rpm, maintained for 45 s; and the sample is heated at 200°C for 60 min in a vacuum drying oven to obtain a PI film with a thickness of 2 μm, which is used to further improve the step slope.

[0132] Figure 3 In step 4, AZ9620 photoresist is spin-coated onto the surface of the PI film with the bump structure. After pre-baking, UV exposure using a first mask, and development, a photoresist layer with recording sites, metal interconnects, and a pad array pattern is formed, wherein the recording site pattern is located on the surface of the bump structure. A metal layer is then deposited, comprising an adhesive layer and a detection electrode array. After spin-coating the photoresist, the adhesive layer is deposited first, followed by the detection electrode array. The deposition process is set to Ti first, then Au, and the crucible is changed during the deposition process. The spin-coating speed is 4500 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 300 s. The adhesive layer is made of titanium and has a thickness of 10 nm. The detection electrode array is made of gold and has a thickness of 50 nm. The slope of the recording sites is 160°. After depositing the detection electrode array, the sample is immersed in acetone to remove residual photoresist.

[0133] Figure 3 In step 5, a third layer of polyimide (PI) and pyrrolidone mixture is spin-coated onto the surface of the above-mentioned surface detection electrode array. The initial rotation speed is 500 rpm, maintained for 5 s; the stable rotation speed is 2500 rpm, maintained for 45 s; and then it is heated and cured at 200℃ for 120 min.

[0134] Figure 3 In step 6, AZ4620 photoresist is spin-coated onto the surface of the PI film. The initial spin speed is 500 rpm, maintained for 5 s; the stable spin speed is 2500 rpm, maintained for 45 s; preheating is carried out at 95°C for 2 min; exposure is carried out for 8 s; and development is carried out for 290 s.

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

[0136] Example 2

[0137] like Figure 5 As shown in the figure, this embodiment provides a simple method for fabricating a ring-shaped protrusion electrode. The specific fabrication method is as follows:

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

[0139] AZ4620 photoresist was spin-coated onto the surface of the PI film. The initial spin speed was 500 rpm, maintained for 5 seconds; the stable spin speed was 2500 rpm, maintained for 60 seconds; and the film was heated at 100°C for 3 minutes to obtain a photoresist layer with a thickness of 8 μm. The film was then exposed to UV light (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 sample was etched using RIE (Rear Injection) with oxygen as the etching gas, an etching power of 60W, an etching time of 20 minutes, and an etching pressure of 40Pa. The exposed PI was thoroughly etched to form a square bump structure with a height of 5μm. The sample was then sequentially ultrasonicated with acetone and isopropanol, rinsed with deionized water, and the resist was removed.

[0141] A second layer of PI and pyrrolidone mixture was spin-coated onto the surface of the sample with the bump structure array. The initial rotation speed was 500 rpm, maintained for 5 s; the stable rotation speed was 2700 rpm, maintained for 45 s; and the sample was heated at 200°C for 60 min in a vacuum drying oven to obtain a PI film with a thickness of 3 μm, which was used to further improve the step slope.

[0142] The above samples were spin-coated with AZ4620 photoresist, initially at 500 rpm for 5 seconds, then stabilized at 2500 rpm for 60 seconds, followed by baking at 100°C for 3 minutes. Exposure was performed using the first photomask for 10 seconds, followed by development for 215 seconds. The samples were then rinsed with deionized water and dried with a nitrogen gun.

[0143] Ti / Au were deposited by electron beam evaporation to thicknesses of 10 / 100 nm. The deposited samples were then immersed in acetone for 20 minutes. After a large area of ​​the adhesive had peeled off, the samples were sequentially immersed in acetone and isopropanol and sonicated. They were then rinsed with deionized water and dried with a nitrogen gun. The slope of the recording sites was 140°.

[0144] SU-8 2005 photoresist was spin-coated onto the surface of the sample. The initial spin speed was 500 rpm, maintained for 5 seconds; the stable spin speed was 2000 rpm, maintained for 60 seconds; and the sample was heated at 95°C for 2 minutes, resulting in a film thickness of approximately 5 μm. The sample was then exposed using a second mask for 150 seconds, developed, fixed, and dried with high-pressure nitrogen to obtain a 2.5 μm encapsulation layer.

[0145] The recording electrode is released by electrochemical corrosion or dilute hydrochloric acid corrosion of the aluminum sacrificial layer.

Claims

1. A bump electrode characterized by, The bump electrode comprises: a flexible substrate, a surface of which has an array of bump structures; a flexible layer disposed on the surface of the flexible substrate having the array of bump structures; an array of detection electrodes on the surface of the flexible layer, each detection electrode comprising a recording site, a wire and a pad, one end of the wire being connected to the recording site, the other end of the wire being connected to the pad, each recording site corresponding to a bump structure, and the recording site covering the top and side of the bump structure; an encapsulation layer covering the array of detection electrodes except the recording sites. The flexible layer controls the slope of the recording site to be 110°-170°, the slope of the recording site being the included angle between the top and side of the recording site.

2. The bump electrode according to claim 1, wherein The bump electrode has one or more of the following characteristics: 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 array of detection electrodes 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, parylene and polyimide.

3. The bump electrode according to claim 1, wherein The bump electrode has one or more of the following characteristics: 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 array of detection electrodes is 50-500 nm; The thickness of the encapsulation layer is 1-20 μm.

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

5. The bump electrode according to claim 4, wherein The material of the adhesive layer is selected from one or more of titanium, chromium and titanium-tungsten alloy; and / or, the thickness of the adhesive layer is 10-100 nm.

6. A method of producing the bump electrode according to any one of claims 1 to 5, characterized by, The method comprises the following steps: (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 prepared in step (3) to remove the first photoresist bump array, thereby obtaining a flexible substrate having an array of bump structures; (5) preparing a flexible layer on the surface of the flexible substrate; (6) preparing an array of detection electrodes on the surface of the flexible layer, the recording sites being located above and on the side of the bump structures, and the wires and pads being located above the non-bump structures; (7) preparing an encapsulation layer on the surface of the sample prepared in step (6), the encapsulation layer not covering the recording sites.

7. The method of claim 6, wherein, In step (6), before preparing the array of detection electrodes, an adhesive layer is first evaporated.

8. The method of claim 6, wherein, The method further comprises step (8): removing the metal sacrificial layer and the carrier.

9. The method of any one of claims 6-8, wherein, The method has one or more of the following characteristics: 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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