Neural stimulation electrode based on titanium nitride film and method of making the same
Titanium nitride thin films were prepared at low temperatures using magnetron reactive sputtering, which solved the problems of electrode inhomogeneity and weak bonding caused by high-temperature preparation. This resulted in high-performance, long-term stable nerve stimulation electrodes suitable for the treatment of nervous system diseases.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- HEZE QIYUAN (BEIJING) TECH CO LTD
- Filing Date
- 2025-12-22
- Publication Date
- 2026-08-04
AI Technical Summary
In the existing technology, the preparation method of titanium nitride thin film requires high temperature, which leads to uneven electrode material and weak bonding force, affecting the stability and life of the electrode. In addition, commonly used materials such as platinum and iridium oxide have problems such as limited charge injection capacity or insufficient long-term stability.
Titanium nitride thin films were prepared at low temperatures using magnetron reactive sputtering. Metal stacks were deposited by sputtering at temperatures below 100°C and then cured at high temperatures to recrystallize the titanium nitride thin films, forming high-performance stimulation sites.
A titanium nitride thin film neurostimulation electrode with high adhesion, low interfacial impedance, and good long-term stability was successfully prepared at low temperature. It has excellent biocompatibility and charge injection capacity and is suitable for mass production.
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Figure CN121490269B_ABST
Abstract
Description
Technical Field
[0001] This disclosure belongs to the field of biomedical engineering and microfabrication technology, and relates to neural stimulation electrode technology, specifically to a neural stimulation electrode based on titanium nitride thin film and its preparation method. Background Technology
[0002] Neurostimulation techniques, such as deep brain stimulation, spinal cord stimulation, cochlear implants, and retinal prostheses, have become important means of treating neurological diseases (such as Parkinson's disease, epilepsy, blindness, and deafness). The core component of these techniques is the neurostimulation electrode, which functions to exchange charges with nerve tissue under the action of electrical pulses, thereby activating or inhibiting nerve signals.
[0003] An ideal neurostimulation electrode should possess low interfacial impedance, high charge injection capacity, long-term electrochemical stability, and excellent biocompatibility. Currently, commonly used electrode materials include platinum, iridium, and their oxides. Platinum has good biocompatibility, but its charge injection capacity is limited; iridium oxide has a high charge injection capacity, but there is a risk of film peeling under long-term pulse stimulation.
[0004] Titanium nitride (TiN), as a ceramic material, possesses metallic conductivity, extremely high hardness, good chemical inertness, and biocompatibility, making it a highly promising electrode material. Traditional methods for preparing titanium nitride, such as chemical vapor deposition (CVD), require high deposition temperatures, typically at least above 500°C, which may damage the fabricated micro-electrode structure. Meanwhile, titanium nitride films prepared using general physical vapor deposition (PVD) methods often suffer from compositional inhomogeneity, poor density, and weak adhesion to the substrate, affecting the electrode's stability and lifespan.
[0005] Therefore, there is an urgent need for a new technology that can fabricate high-performance, high-reliability titanium nitride thin film-based neurostimulation electrodes at lower temperatures. Summary of the Invention
[0006] The purpose of this disclosure is to provide a neurostimulation electrode based on a titanium nitride thin film and its preparation method. This disclosure can overcome the shortcomings of high-temperature deposition in the prior art, and provide a method for preparing a neurostimulation electrode with excellent crystallinity, high adhesion, low interfacial impedance, high charge injection capacity, good long-term stability and excellent biocompatibility by magnetron reactive sputtering at a lower temperature.
[0007] In a first aspect, this disclosure provides a method for preparing a neurostimulation electrode based on a titanium nitride thin film, comprising:
[0008] A conductive metal layer is fabricated on a lower insulating substrate, and a first photoresist with windows is formed on the conductive metal layer;
[0009] In the windowed area of the first photoresist, at a first temperature, a metal stack is sputtered and deposited by magnetron reactive sputtering to form stimulation sites electrically interconnected with the conductive metal layer on the lower insulating substrate, wherein the metal stack comprises at least a titanium nitride film, and the first temperature is below 100°C.
[0010] The first photoresist is removed by a stripping process;
[0011] A polymer material is coated on the lower insulating substrate, the conductive metal layer thereon, and the stimulation site, and cured at a second temperature above 300°C to form an upper insulating substrate. The curing process causes the titanium nitride film to recrystallize.
[0012] The upper insulating substrate is patterned to expose the stimulation sites.
[0013] In some optional embodiments, the step of sputtering and depositing the metal stack includes: sequentially depositing a titanium adhesion layer, a titanium nitride film, and an aluminum temporary protective layer in the windowed region of the first photoresist, wherein the titanium adhesion layer and the titanium nitride film constitute the stimulation site.
[0014] In some alternative embodiments, the first temperature is 80±5°C during the sputtering deposition of the metal stack.
[0015] In some alternative embodiments, the sputtering deposition process of the titanium nitride film is carried out in a mixed atmosphere of argon and nitrogen, wherein the flow rate ratio of nitrogen to argon is 4:1 to 8:1.
[0016] In some optional embodiments, the neural stimulation electrode is divided into a precursor portion and a pad portion, the stimulation site is located in the precursor portion, and the conductive metal layer includes a pad located in the pad portion and metal traces electrically connecting the pad and the stimulation site; the step of patterning the upper insulating substrate includes: forming and patterning an aluminum hard mask layer on the upper insulating substrate, the patterned aluminum hard mask layer exposing the portion corresponding to the stimulation site, the portion corresponding to the pad, and the portion of the precursor portion that needs to be cut out; performing dry etching to expose the stimulation site and the pad, and forming a cutout pattern in the precursor portion.
[0017] In some alternative embodiments, after the step of patterning the upper insulating substrate, the method further includes: removing the aluminum hard mask layer located at the pad portion to expose the upper insulating substrate for bonding; and after bonding is completed, removing the aluminum hard mask layer located at the metal trace portion and the aluminum temporary protective layer located at the stimulation site portion.
[0018] In some alternative embodiments, the step of fabricating a conductive metal layer on a lower insulating substrate includes: providing a carrier made of silicon oxide; coating the carrier with a polymer material and curing it at a third temperature of not less than 300°C to form a lower insulating substrate; forming a second photoresist with windows on the lower insulating substrate; sequentially depositing a titanium layer and a gold layer in the windowed areas of the second photoresist to form the conductive metal layer; and removing the second photoresist by a stripping process.
[0019] In some alternative embodiments, prior to the step of sputtering and depositing the metal stack, the method further includes: pre-sputtering a titanium target source in an argon atmosphere to remove the oxide layer on the surface of the titanium target.
[0020] In some alternative embodiments, prior to the pre-sputtering step, the method further includes plasma cleaning of the windowed area of the first photoresist.
[0021] In a second aspect, this disclosure provides a neurostimulation electrode based on a titanium nitride thin film, prepared by the method described in the first aspect. The neurostimulation electrode includes: a lower insulating substrate; a metal trace layer disposed on the lower insulating substrate; stimulation sites disposed on the lower insulating substrate and electrically interconnected with the metal trace layer, the stimulation sites including a titanium nitride thin film; and an upper insulating layer covering the metal trace layer and exposing the stimulation sites.
[0022] This disclosure proposes a neurostimulation electrode based on titanium nitride thin film and its preparation method. By sputtering and depositing a metal stack including titanium nitride thin film at a first temperature using a magnetron reactive sputtering process to form stimulation sites, and by using a curing process at a second temperature to recrystallize the titanium nitride thin film, a high-performance and high-reliability neurostimulation electrode based on titanium nitride thin film can be prepared at a lower temperature.
[0023] Compared with the prior art, the beneficial effects of the present invention include:
[0024] ① Lower deposition temperature: Low-temperature deposition of titanium nitride thin films was achieved below 100℃;
[0025] ② Excellent electrical properties: Titanium nitride thin films prepared by magnetron reactive sputtering have low resistivity, which can significantly reduce the electrode-electrolyte interface impedance, improve charge injection capacity, and make stimulation more effective and safer;
[0026] ③ Excellent stability: Titanium nitride thin films are extremely chemically stable, corrosion-resistant, oxidation-resistant, and can withstand long-term electrochemical pulse stimulation, thus extending the service life of the electrodes;
[0027] ④ Good biocompatibility: Titanium nitride has no toxic side effects on human tissues and has good biocompatibility;
[0028] ⑤ Strong process compatibility: Magnetron sputtering is a low-temperature process that will not cause thermal damage to the microelectrode structure prepared in the early stage. It has good compatibility with modern microfabrication technology and is suitable for mass production.
[0029] ⑥ High film quality: Through parameter optimization, the obtained film is dense, uniform, has strong adhesion, and reliable performance. Attached Figure Description
[0030] Other features, objects, and advantages of this disclosure will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings. The drawings are for illustrative purposes only and are not intended to limit the invention. In the drawings:
[0031] Figure 1 This is a top view schematic diagram of a neurostimulation electrode based on a titanium nitride thin film according to an embodiment of the present disclosure;
[0032] Figure 2 This is a partial cross-sectional view of a neurostimulation electrode based on a titanium nitride thin film according to an embodiment of this disclosure.
[0033] Figure 3 This is a schematic flowchart of a method for preparing a neurostimulation electrode based on a titanium nitride thin film according to an embodiment of this disclosure.
[0034] Figure 4 This is a schematic diagram of the finished product effect of a neurostimulation electrode based on a titanium nitride thin film according to an embodiment of the present disclosure;
[0035] Figure 5 This is a schematic diagram of a partial effect of a neurostimulation electrode based on a titanium nitride thin film according to an embodiment of the present disclosure;
[0036] Figure 6 This is a schematic diagram of the cyclic voltammetry (CV) test results for the neurostimulation electrodes disclosed herein;
[0037] Figure 7 This is a schematic diagram of the impedance test results for the neurostimulation electrodes disclosed herein.
[0038] Figure label:
[0039] 100: Carrier; 110: Lower insulating substrate; 111: Titanium layer; 112: Gold layer; 120: Metal trace; 130: Pad; 140: Stimulation site; 141: Titanium adhesion layer; 142: Titanium nitride film; 143: Aluminum temporary protective layer; 150: Upper insulating substrate; 160: Hollow pattern; 200: Precursor section; 300: Pad section. Detailed Implementation
[0040] The present disclosure will now be described in further detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and not intended to limit it. Furthermore, it should be noted that, for ease of description, only the parts relevant to the invention are shown in the accompanying drawings.
[0041] It should be readily understood that the meanings of “on,” “above,” and “on top of” in this disclosure should be interpreted in the broadest sense, such that “on” means not only “directly on something,” but also “on something” including intermediate components or layers existing between the two.
[0042] Furthermore, for ease of description, spatial relative terms such as “below,” “under,” “lower,” “above,” and “upper” may be used herein to describe the relationship of one component or part to another component or part shown in the accompanying drawings. In addition to the orientations described in the figures, spatial relative terms are also intended to cover different orientations of the device during use or operation. The device may be oriented in other ways (rotated 90° or otherwise), and the spatial relative descriptive terms used herein may be interpreted accordingly.
[0043] It should be noted that the structures, proportions, sizes, etc., depicted in the accompanying drawings are only for illustrative purposes to aid those skilled in the art in understanding and reading the content described herein, and are not intended to limit the implementation conditions of this disclosure. Therefore, they have no substantial technical significance. Any modifications to the structure, changes in proportions, or adjustments to size, without affecting the effectiveness and purpose of this disclosure, should still fall within the scope of the technical content disclosed herein. Furthermore, terms such as "above," "first," "second," and "a" used in this specification are merely for clarity of description and are not intended to limit the scope of this disclosure. Changes or adjustments to their relative relationships, without substantially altering the technical content, should also be considered within the scope of this disclosure's implementation.
[0044] It should be noted that, unless otherwise specified, the embodiments and features described in this disclosure can be combined with each other. This disclosure will now be described in detail with reference to the accompanying drawings and embodiments.
[0045] refer to Figures 1 to 3 One embodiment of this disclosure proposes a neurostimulation electrode based on titanium nitride thin film and a method for its preparation.
[0046] like Figure 1 and Figure 2As shown, the titanium nitride thin film-based neurostimulation electrode (hereinafter referred to as the neurostimulation electrode or electrode) of this disclosure, in cross-sectional view, may include, from bottom to top, a lower insulating substrate 110, a conductive metal layer (including metal traces 120 and pads 130), stimulation sites 140, and an upper insulating substrate 150. In top view, the neurostimulation electrode of this disclosure can be divided into a precursor portion 200 and a pad portion 300. The precursor portion 200 includes multiple stimulation sites 140 for implantation into biological tissue; the pad portion 300 includes multiple pads 130 for bonding to a substrate. One end of the metal trace 120 extends to the precursor portion 200 to electrically connect to the stimulation sites 140, and the other end extends to the pad portion 300 to connect to the pads 130, such that the pads 130 and the stimulation sites 140 are electrically interconnected through the metal trace 120.
[0047] The stimulation site 140 is exposed from the upper insulating substrate 150, and the stimulation site 140 includes a titanium nitride thin film 142 sputtered and deposited by magnetron reactive sputtering.
[0048] The pre-drive portion 200 includes multiple hollow patterns 160, which can be enclosed and defined by metal traces 120 and stimulation sites 140. The upper insulating substrate 150 and the lower insulating substrate 110 at the hollow pattern are removed to achieve a through-hole.
[0049] In this invention, the lower insulating substrate 110 of the neurostimulation electrode can be disposed on a carrier 100, with the carrier 100 supporting the entire neurostimulation electrode. The carrier 100 can be removed before the neurostimulation electrode is implanted into biological tissue.
[0050] The lower insulating substrate 110 and the upper insulating substrate 150 can be formed using polymer materials, including but not limited to polyimide (PI). The conductive metal layer (including metal traces 120 and pads 130) can be formed using one or more metal layers. For example, it can include a titanium (Ti) layer 111 deposited on the lower insulating substrate 110 and a gold (Au) layer 112 deposited on the titanium layer 111. The stimulation site 140 can be formed using one or more metal layers. For example, it can include a titanium adhesion layer 141 deposited on the lower insulating substrate 110 and a titanium nitride film 142 deposited on the titanium adhesion layer 141. For example, it can also include an aluminum temporary protective layer 143 deposited on the titanium nitride film 142, which will be removed before electrode implantation. The carrier 100 includes, but is not limited to, a carrier made of silicon oxide.
[0051] refer to Figure 3The method for fabricating a neurostimulation electrode based on a titanium nitride thin film disclosed herein is a method based on a magnetron reactive sputtering process, which may include the following steps:
[0052] The first stage, sample preparation: A conductive metal layer is fabricated on the underlying insulating substrate, and a first photoresist with windows is formed on the conductive metal layer. Specifically, this may include the following steps:
[0053] Step S1: Provide a carrier made of silicon oxide; coat the carrier with a polymer material (e.g., PI) and bake and cure it at a third temperature to form a lower insulating substrate, wherein the third temperature is not lower than 300°C and not higher than 350°C.
[0054] Step S2: Form a second photoresist with windows on the lower insulating substrate. For example, a double-layer photoresist can be coated, and patterned by photolithography and development to form windows corresponding to the metal line regions.
[0055] Step S3: In the windowed area of the second photoresist, a titanium layer and a gold layer are deposited sequentially to form a conductive metal layer. For example, a titanium layer is deposited first, with a thickness of 5nm-10nm; then a gold layer is deposited, with a thickness of ≥100nm.
[0056] Step S4: Remove the second photoresist by lift-off process, thus forming the conductive metal layer.
[0057] Step S5: Form a first photoresist with windows on top of the conductive metal layer. For example, a double-layer photoresist can be coated, and patterned by photolithography and development to form windows corresponding to the stimulation sites. This step exposes the stimulation sites by covering other areas with the first photoresist, preparing for the subsequent sputtering deposition process. This completes the sample preparation.
[0058] The second stage, sputtering deposition: In the windowed area of the first photoresist, a metal stack comprising at least a titanium nitride thin film is sputtered and deposited using a magnetron reactive sputtering process to form stimulation sites. Specifically, this may include the following steps:
[0059] Step S6: Place the prepared sample into a plasma cleaning device. The device uses an Ar / O2 mixed gas to perform plasma cleaning on the sample surface, mainly targeting the windowed areas of the first photoresist. For example, the plasma cleaning conditions can be 80W for 1-3 minutes. The purpose of cleaning is primarily to remove residual photoresist and increase the adhesion of the sample, thereby increasing the adhesion between the subsequently deposited titanium nitride film and the underlying metal (conductive metal layer).
[0060] Step S7: In an argon atmosphere, turn on the titanium target source for pre-sputtering to remove the oxide layer on the surface of the titanium target. Specific steps may include:
[0061] The cleaned sample was fixed on a water-cooled sample stage and placed into the vacuum chamber of the magnetron reactive sputtering equipment. The vacuum chamber was then evacuated to a background vacuum level of ≤8.0×10⁻⁶. -4 Pa, heats the equipment to 80℃.
[0062] High-purity argon gas is introduced into the vacuum chamber to maintain the pressure at 0.5 Pa.
[0063] Turn on the RF power supply and adjust the power to 150W. Turn on the titanium target source and pre-sputter for 3 minutes to remove the oxide layer and other impurities from the surface of the titanium target. During this pre-sputtering process, a baffle can be used to block the sample.
[0064] Step S8: In the windowed region of the first photoresist, at a first temperature, a metal stack is deposited by magnetron reactive sputtering to form stimulation sites electrically interconnected with the conductive metal layer on the underlying insulating substrate. Specific steps may include:
[0065] After pre-sputtering is completed, the sample baffle is opened, and a titanium layer is deposited in the window area of the first photoresist as a titanium adhesion layer. Optionally, the thickness of the titanium adhesion layer is ≤10nm.
[0066] After the titanium adhesion layer is deposited, nitrogen gas is introduced with a nitrogen to argon flow rate ratio of 4:1 to 8:1 to start the reaction sputtering of titanium nitride film on the titanium adhesion layer with a target thickness of ≥600nm.
[0067] Next, a 30nm Al layer can be deposited on the titanium nitride film as a temporary aluminum protective layer, which can act as an antioxidant layer. This completes the fabrication of the stimulation site, which consists of a titanium adhesion layer and a titanium nitride film. The temporary aluminum protective layer will be removed during subsequent implantation.
[0068] Step S9: Remove the first photoresist by lift-off process to complete metal patterning and shape the stimulation sites.
[0069] Step S10: A polymer material is coated onto the lower insulating substrate, the conductive metal layer thereon, and the stimulation sites, and then cured at a second temperature to form the upper insulating substrate. Here, the polymer material can be polyimide (PI), which can be coated by spin coating. The second temperature is above 300°C, and can reach a maximum of 350°C. This curing process allows the titanium nitride film to recrystallize further, resulting in a more stable titanium nitride film.
[0070] Step S11: Pattern the upper insulating substrate to expose the stimulation sites and pads, and form a cutout pattern.
[0071] Specifically, the step of patterning the upper insulating substrate may include:
[0072] Aluminum is deposited on the upper insulating substrate to form an aluminum hard mask layer and pattern it. The patterned aluminum hard mask layer exposes the areas corresponding to the stimulation sites, the areas corresponding to the pads, and the areas of the precursor that need to be cut out.
[0073] Dry etching is performed to expose the stimulation sites and pads, and a hollow pattern is formed in the precursor.
[0074] Here, it should be noted that the nerve stimulation electrode is divided into a precursor part and a pad part. The stimulation site is located in the precursor part, and the conductive metal layer includes the pads located in the pad part and the metal traces that electrically connect the pads and the stimulation site.
[0075] Phase 3: Follow-up processing.
[0076] Step S12: The wafer is diced into smaller pieces using a dicing process to obtain a complete single electrode. While the first and second stages described above can involve batch fabrication of multiple electrodes on a single wafer, this step uses dicing to cut and obtain individual electrodes.
[0077] Step S13: Remove the aluminum hard mask layer located on the pads to expose the upper insulating substrate for bonding. For example, the pads can be bonded to various types of substrates such as printed circuit boards (PCBs) and flexible printed circuit boards (FPCs). Optionally, after bonding, underfill adhesive can be filled into the gap between the electrodes and the substrate to protect the electrical connection structure and enhance the connection strength.
[0078] Step S14: After bonding is complete, remove the aluminum hard mask layer located at the metal trace and the aluminum temporary protective layer located at the stimulation site. (Reference) Figure 4 and 5 The diagram shows the effect of the prepared neurostimulation electrode.
[0079] At this point, the fabrication of the entire neurostimulation electrode is complete. The soft neurostimulation electrode is now supported by a rigid carrier for easy transport and storage; the rigid carrier can be removed before electrode implantation.
[0080] The above describes the neurostimulation electrode based on titanium nitride thin film and its preparation method as proposed in this disclosure. The neurostimulation electrode of this disclosure is characterized by the following structure, from bottom to top: a biocompatible flexible or rigid lower insulating substrate, a conductive metal layer (such as Au, Pt), stimulation sites including a titanium nitride thin film prepared by magnetron reactive sputtering, and a biocompatible flexible or rigid upper insulating substrate.
[0081] The key processes of the preparation method disclosed herein include:
[0082] High vacuum environment: Ensure a high background vacuum level, reduce impurity contamination, and maintain a vacuum level ≤8.0×10-4Pa;
[0083] Precise gas control: By precisely controlling the flow ratio of argon to nitrogen, reactive sputtering of the titanium target is achieved, generating a titanium nitride thin film with an optimal stoichiometric ratio close to 1:1 suitable for the stimulation electrode (i.e., the molar ratio of nitrogen to titanium is 1:1), which is the key to obtaining low resistivity.
[0084] Optimized process parameters: By optimizing sputtering power, working gas pressure and substrate temperature, high-quality films with dense, uniform texture and strong adhesion to the underlying metal can be obtained at lower temperatures.
[0085] refer to Figure 6 The figure shows a schematic diagram of the cyclic voltammetry (CV) test results for the neurostimulation electrode of this disclosure. In the figure, the horizontal axis represents voltage and the vertical axis represents current. The curves in the figure show the redox behavior of the electrode material. The area under the curve is related to the amount of charge transferred by the electrode material during oxidation and reduction. It can be seen from the figure that the neurostimulation electrode of this disclosure has good charge injection capability and good reversibility and stability.
[0086] refer to Figure 7 The figure shows a schematic diagram of the impedance test results for the neural stimulation electrode of the present disclosure. As can be seen from the figure, the neural stimulation electrode of the present disclosure has an impedance of ≤100KΩ in a PBS standard solution (e.g., physiological saline, whose composition is similar to human body fluids) at a frequency of 1000Hz, and has good biocompatibility.
[0087] This disclosure also includes stability tests. In PBS solution, at a 20-micrometer site, the fatigue stimulation number of 50 microamps per voltammeter was greater than 100 million times, demonstrating that the nerve stimulation electrode of this disclosure has extremely high reliability.
[0088] The above description is merely a preferred embodiment of this disclosure and an explanation of the technical principles employed. Those skilled in the art should understand that the scope of this disclosure is not limited to technical solutions formed by specific combinations of the above-described technical features, but should also cover other technical solutions formed by arbitrary combinations of the above-described technical features or their equivalents without departing from the above-described concept. For example, technical solutions formed by substituting the above features with (but not limited to) technical features disclosed in this disclosure that have similar functions.
Claims
1. A method for preparing a neurostimulation electrode based on a titanium nitride thin film, characterized in that, include: A conductive metal layer is fabricated on a lower insulating substrate, and a first photoresist with windows is formed on the conductive metal layer; In the windowed area of the first photoresist, at a first temperature, a metal stack is sputtered and deposited by magnetron reactive sputtering to form stimulation sites electrically interconnected with the conductive metal layer on the lower insulating substrate, wherein the metal stack comprises at least a titanium nitride film, and the first temperature is below 100°C. The first photoresist is removed by a stripping process; A polymer material is coated on the lower insulating substrate, the conductive metal layer thereon, and the stimulation site, and cured at a second temperature above 300°C to form an upper insulating substrate. The curing process causes the titanium nitride film to recrystallize. The upper insulating substrate is patterned to expose the stimulation sites.
2. The method according to claim 1, characterized in that, The step of sputtering and depositing the metal stack includes: sequentially depositing a titanium adhesion layer, a titanium nitride thin film, and an aluminum temporary protective layer in the windowed area of the first photoresist, wherein the titanium adhesion layer and the titanium nitride thin film constitute the stimulation site.
3. The method according to claim 2, characterized in that, During the sputtering deposition of the metal stack, the first temperature is 80±5℃.
4. The method according to claim 2, characterized in that, The sputtering deposition process of the titanium nitride thin film is carried out in a mixed atmosphere of argon and nitrogen, wherein the flow ratio of nitrogen to argon is 4:1 to 8:
1.
5. The method according to claim 2, characterized in that, The neural stimulation electrode is divided into a precursor portion and a pad portion. The stimulation site is located in the precursor portion. The conductive metal layer includes pads located in the pad portion and metal traces electrically connecting the pads and the stimulation site. The step of patterning the upper insulating substrate includes: An aluminum hard mask layer is formed and patterned on the upper insulating substrate. The patterned aluminum hard mask layer exposes the portions corresponding to the stimulation sites, the portions corresponding to the pads, and the portions of the precursor that need to be cut out. Dry etching is performed to expose the stimulation sites and the pads, and a hollow pattern is formed in the precursor portion.
6. The method according to claim 5, characterized in that, After the step of patterning the upper insulating substrate, the method further includes: Remove the aluminum hard mask layer located on the pad portion to expose the upper insulating substrate for bonding; After bonding is completed, the aluminum hard mask layer located at the metal trace and the aluminum temporary protective layer located at the stimulation site are removed.
7. The method according to claim 1, characterized in that, The steps for fabricating a conductive metal layer on a lower insulating substrate include: Provide a carrier made of silicon dioxide; A polymer material is coated onto the carrier and cured at a third temperature of not less than 300°C to form a lower insulating substrate. A second photoresist with windows is formed on the lower insulating substrate; In the windowed area of the second photoresist, a titanium layer and a gold layer are deposited sequentially to form the conductive metal layer; The second photoresist is removed by a stripping process.
8. The method according to claim 1, characterized in that, Prior to the step of sputtering and depositing the metal stack, the method further includes: pre-sputtering a titanium target source in an argon atmosphere to remove the oxide layer on the surface of the titanium target.
9. The method according to claim 8, characterized in that, Before the pre-sputtering step, the method further includes: performing plasma cleaning on the windowed area of the first photoresist.
10. A neurostimulation electrode based on a titanium nitride thin film, characterized in that, The neural stimulation electrode is prepared by the method of any one of claims 1 to 9, comprising: Lower insulating substrate; A metal trace layer disposed on the lower insulating substrate; Stimulation sites disposed on the lower insulating substrate and electrically interconnected with the metal trace layer, the stimulation sites comprising a titanium nitride thin film; and, An upper insulating layer covers the metal trace layer and exposes the stimulation site.