Forming method of porous titanium electrode with high aspect ratio for micro supercapacitor
By forming a multi-layer photoresist layer on the substrate and performing physical vapor deposition and selective etching, the problem of limited depth and aspect ratio of metal electrodes is solved, and the molding of high-deep and aspect ratio porous titanium electrodes is achieved, which improves the performance of the micro supercapacitor and reduces costs.
Patent Information
- Application Number
- CN202211461580.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2022-11-17
- Publication Date
- 2025-05-02
- Estimated Expiration
- 2042-11-17
AI Technical Summary
In the prior art, the aspect ratio of metal electrodes is limited, and the high aspect ratio cannot be achieved, which in turn limits the performance of the micro supercapacitor.
By forming a first photoresist layer and a second photoresist layer that are adhered to each other on the substrate, and forming a titanium-based alloy electrode during physical vapor deposition, and then selective etching is performed using an etchant to remove other elements other than titanium to form a high-deep and aspect ratio porous titanium electrode.
The molding of high-deep and aspect ratio porous titanium electrodes is achieved, which improves the capacitance density and frequency performance of micro supercapacitors, while reducing costs, and has the characteristics of being highly simplified and highly compatible with CMOS standard processes.
Smart Images
Figure CN115798944B_ABST
Abstract
Description
Technical Field
[0001] The invention relates to the technical field of supercapacitors, and in particular to a method for forming a porous titanium electrode with a high aspect ratio for a micro supercapacitor. Background Art
[0002] With the development and application of advanced micro-nano processing technology, chip and system integration, and advanced packaging technology, the further miniaturization of integrated circuits has become an inevitable trend. However, among all relevant board-level or wafer-level integrated circuits, the huge and non-integrated electrolytic capacitors have seriously hindered the further development of integrated circuits. Wafer-level micro-supercapacitors have become one of the most promising alternatives to electrolytic capacitors due to their small size and high performance. Among them, the formation and preparation of electrodes is one of the important factors that determine the performance of micro-supercapacitors. At present, the molding methods widely used in the manufacture of micro-supercapacitor electrodes mainly include the following: chemical vapor deposition, printing technology, laser scribing, self-assembly, physical vapor deposition and other thin film molding technologies. Among them, physical vapor deposition is often used to prepare metal electrode structures.
[0003] However, in the existing metal electrode manufacturing, the thickness of the metal electrode deposited by physical vapor deposition is usually required to be less than one-third of the thickness of the photoresist layer in order to successfully use the lift-off process to achieve the patterning of the metal electrode. Generally speaking, the thickness of the photoresist layer used for metal lift-off is usually around 1 micron to 2 microns. Therefore, the thickness of the metal electrode formed by the traditional manufacturing method is also limited to less than 1 micron, which cannot meet the requirements of high aspect ratio, thereby limiting the performance of the micro supercapacitor. Summary of the invention
[0004] The present invention provides a method for forming a micro-supercapacitor porous titanium electrode with a high aspect ratio, which is used to solve the defect that the aspect ratio of metal electrodes in the prior art is limited, realize a high aspect ratio metal electrode, and thus enhance the performance of the micro-supercapacitor.
[0005] The present invention provides a method for forming a micro-supercapacitor porous titanium electrode with a high aspect ratio, comprising:
[0006] A photolithography step, in which a first photoresist layer and a second photoresist layer adhering to each other are formed on a substrate by photolithography, wherein a cross-sectional area of the first photoresist layer is smaller than a cross-sectional area of the second photoresist layer along a direction parallel to the substrate;
[0007] A sputtering step, in which a titanium-based alloy is subjected to physical vapor deposition to form a titanium-based alloy electrode;
[0008] An etching step, in which an etchant is used to selectively etch the titanium-based alloy electrode to remove elements other than titanium in the titanium-based alloy electrode to form a porous titanium electrode with a high aspect ratio.
[0009] A method for forming a micro-supercapacitor porous titanium electrode with a high aspect ratio provided by the present invention also includes:
[0010] A stripping step, in which a stripping agent is used to remove the first photoresist layer, the second photoresist layer and the inverted trapezoidal porous titanium electrode structure deposited on the second photoresist layer.
[0011] According to a method for forming a micro-supercapacitor high aspect ratio porous titanium electrode provided by the present invention, the aspect ratio of the high aspect ratio porous titanium electrode is 0.1 to 0.4.
[0012] According to a method for forming a micro-supercapacitor high aspect ratio porous titanium electrode provided by the present invention, the mass percentage of titanium in the titanium-based alloy is 10% to 70%.
[0013] According to a method for forming a micro-supercapacitor high aspect ratio porous titanium electrode provided by the present invention, the mass percentage of titanium in the titanium-based alloy is 30%, and the mass percentage of aluminum is 70%.
[0014] According to a method for forming a micro-supercapacitor high aspect ratio porous titanium electrode provided by the present invention, in the sputtering step, the titanium-based alloy is suitable for forming an inverted trapezoidal structure with the second photoresist layer as the base and a regular trapezoidal structure with the substrate as the base.
[0015] According to a method for forming a micro-supercapacitor porous titanium electrode with a high aspect ratio provided by the present invention, the first photoresist layer adopts AR-BR 5480, and the second photoresist layer adopts AZ601.
[0016] According to a method for forming a micro-supercapacitor high aspect ratio porous titanium electrode provided by the present invention, the sum of the thicknesses of the first photoresist layer and the second photoresist layer is 1.8 microns to 2.4 microns.
[0017] According to a method for forming a micro-supercapacitor porous titanium electrode with a high aspect ratio provided by the present invention, the thickness of the titanium-based alloy electrode is 3 microns to 12 microns.
[0018] According to a method for forming a micro-supercapacitor high aspect ratio porous titanium electrode provided by the present invention, the substrate includes a silicon substrate and a silicon dioxide insulating layer.
[0019] The method for forming a micro-supercapacitor porous titanium electrode with a high aspect ratio provided by the present invention is to form a first photoresist layer and a second photoresist layer that are mutually adhered on a substrate, and to set the cross-sectional area of the first photoresist layer to be smaller than the cross-sectional area of the second photoresist layer in a direction parallel to the substrate, so that the titanium-based alloy forms an inverted trapezoidal structure with the second photoresist layer as the bottom and a positive trapezoidal structure with the substrate as the bottom during physical vapor deposition, thereby facilitating the separation of each titanium-based alloy part that is continuously conformally grown on the photoresist layer and the substrate due to its large thickness, thereby realizing the forming and patterning of the porous titanium electrode with a high aspect ratio. The porous titanium electrode with a high aspect ratio formed by the above method can improve the capacitance density and frequency performance of the micro-supercapacitor, and at the same time provide a considerable growth point for subsequent possible pseudocapacitor modification materials. The method is low in cost, and has the characteristics of being highly simplified and highly compatible with CMOS standard processes, so it has the potential for large-scale production in a standard CMOS integrated circuit manufacturing plant. BRIEF DESCRIPTION OF THE DRAWINGS
[0020] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.
[0021] Figure 1 This is one of the flow diagrams of the method for forming a micro-supercapacitor porous titanium electrode with a high aspect ratio provided by an embodiment of the present invention;
[0022] Figure 2 This is the second schematic flow diagram of the method for forming a micro-supercapacitor porous titanium electrode with a high aspect ratio provided by an embodiment of the present invention;
[0023] Figure 3 It is a cross-sectional scanning electron microscope (SEM) characterization diagram of the entire process of etching step and stripping step in the method for forming a micro supercapacitor high aspect ratio porous titanium electrode provided by an embodiment of the present invention;
[0024] Figure 4 This is a SEM characterization of the porous structure surface formed after etching of alloy substrates with different titanium element ratios. DETAILED DESCRIPTION
[0025] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in conjunction with the drawings of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.
[0026] Combine the following Figure 1-Figure 4 The present invention describes a method for forming a micro-supercapacitor porous titanium electrode with a high aspect ratio.
[0027] like Figure 1 As shown, an embodiment of the present invention provides a method for forming a micro-supercapacitor high aspect ratio porous titanium electrode, comprising:
[0028] Step 100: a photolithography step, in which a first photoresist layer and a second photoresist layer adhering to each other are formed on a substrate by photolithography, and a cross-sectional area of the first photoresist layer is smaller than a cross-sectional area of the second photoresist layer along a direction parallel to the substrate;
[0029] Step 200: a sputtering step, in which a titanium-based alloy is subjected to physical vapor deposition to form a titanium-based alloy electrode;
[0030] Step 300: an etching step, in which an etchant is used to selectively etch the titanium-based alloy electrode to remove elements other than titanium in the titanium-based alloy electrode, thereby forming a porous titanium electrode with a high aspect ratio.
[0031] Step 400: a stripping step, in which a stripping agent is used to remove the first photoresist layer, the second photoresist layer and the inverted trapezoidal porous titanium electrode structure deposited on the second photoresist layer.
[0032] The method for forming a micro-supercapacitor porous titanium electrode with a high aspect ratio provided by an embodiment of the present invention is to form a first photoresist layer and a second photoresist layer that are mutually adhered on a substrate, and to set the cross-sectional area of the first photoresist layer to be smaller than the cross-sectional area of the second photoresist layer in a direction parallel to the substrate, so that the titanium-based alloy forms an inverted trapezoidal structure with the second photoresist layer as the bottom and a positive trapezoidal structure with the substrate as the bottom during physical vapor deposition, thereby facilitating the separation of each titanium-based alloy part that is continuously conformally grown on the photoresist layer and the substrate due to its large thickness, thereby realizing the forming and patterning of the porous titanium electrode with a high aspect ratio. The porous titanium electrode with a high aspect ratio formed by the above method can improve the capacitance density and frequency performance of the micro-supercapacitor, and at the same time provide a considerable growth point for subsequent possible pseudocapacitor modification materials. The method is low in cost, highly simplified and highly compatible with CMOS standard processes, and therefore has the potential for large-scale production in standard CMOS integrated circuit manufacturing plants.
[0033] Specifically, in step 100, if Figure 2 As shown, the substrate includes a silicon substrate and a silicon dioxide insulating layer adhered to the silicon substrate. The thickness of the silicon substrate is 400 microns, and the thickness of the silicon dioxide insulating layer is 3000 angstroms. On the substrate, an imaged double-layer photoresist is formed by photolithography, including a first photoresist layer adhered to the substrate, and a second photoresist layer adhered to the first photoresist layer. In other words, the first photoresist layer is located at the bottom layer, and the second photoresist layer is located at the upper layer. In the direction parallel to the substrate, the cross-sectional area of the first photoresist layer is smaller than the cross-sectional area of the second photoresist layer, that is to say, the double-layer photoresist is arranged in a "T" shape as a whole. In the present embodiment, the cross-sectional area of the first photoresist layer along the direction parallel to the substrate is arranged to decrease from bottom to top. By such an arrangement, the titanium-based alloy formed by physical vapor deposition in the subsequent steps can be formed as shown in FIG. Figure 3 The inverted trapezoidal structure with the second photoresist layer as the bottom and the regular trapezoidal structure with the substrate as the bottom shown in a.
[0034] In the present embodiment, the model of the first photoresist layer is AR-BR 5480 (Allresist), and the model of the second photoresist layer is AZ601 (MicroChemicals). The total thickness of the double-layer photoresist, that is, the sum of the thickness of the first photoresist layer and the second photoresist layer, can be 1.8 microns to 2.4 microns. In the present embodiment, 2.4 microns is taken as an example.
[0035] In this embodiment, after step 100, if Figure 2As shown in FIG. 1 , a pure titanium electrode is formed by physical vapor deposition with a thickness of 30 nm. The pure titanium electrode has the functions of both current collector and alloy electrode adhesion layer, that is, it can conduct current and also serve as a carrier of titanium-based alloy to enhance the adhesion ability of titanium-based alloy.
[0036] In step 200, the titanium-based alloy is subjected to physical vapor deposition to form a titanium-based alloy electrode. The physical vapor deposition adopts sputtering technology, the power is 1600 W DC power, and the time is 5 hours. The thickness of the formed titanium-based alloy electrode can be 3 microns to 12 microns, and 10 microns in this embodiment. It is worth mentioning that the prior art generally requires that the thickness of the metal electrode deposited by physical vapor deposition is less than one-third of the thickness of the photoresist layer (0.8 microns in this embodiment), while the thickness of the titanium-based alloy electrode formed in this embodiment is much greater than this value, which creates conditions for realizing a high aspect ratio porous titanium electrode.
[0037] It should be noted that the mass percentage of titanium in the titanium-based alloy can be a value between 10% and 70%. Within this range, the pore size and porosity of the porous electrode can be customizable by changing the proportion of titanium in the titanium-based alloy.
[0038] The forming method of the customizable porous titanium electrode is not limited by the choice of materials. In other words, the remaining elements in the titanium-based alloy can be arbitrarily selected as metals that can be selectively removed by wet etching, thereby increasing the selectivity of the alloy. Figure 4 As shown, by continuously optimizing the porous electrode through a customizable molding method, the optimal pore size / porosity and the corresponding titanium element ratio in the titanium-based alloy that can provide a fast transmission channel for electrons / ions can be further optimized, thereby improving the capacitance density of the micro-supercapacitor. In other words, by changing the mass percentage of titanium in the selected titanium-based alloy, a titanium-based alloy with better performance of the micro-supercapacitor can be optimized.
[0039] In this embodiment, a preferred titanium-based alloy is used, in which the mass percentage of titanium is 30% and the mass percentage of aluminum is 70%.
[0040] like Figure 3 As shown in a, since the cross-sectional area of the first photoresist layer is smaller than the cross-sectional area of the second photoresist layer along the direction parallel to the substrate, and the thickness of the deposited titanium-based alloy is relatively large, the titanium-based alloy will form an inverted trapezoidal structure with the second photoresist layer as the bottom, and a regular trapezoidal structure with the substrate as the bottom. The above-mentioned inverted trapezoidal structure and regular trapezoidal structure are connected. In other words, the titanium-based alloy part on the photoresist layer and the titanium-based alloy part on the substrate are continuously conformally grown.
[0041] In step 300, the titanium-based alloy electrode is selectively etched by using an etchant to remove other elements in the titanium-based alloy electrode except titanium, so as to form a porous titanium electrode with a high aspect ratio. The etchant used is a dilute hydrochloric acid etchant prepared by mixing deionized water and hydrochloric acid in a ratio of 10:1. The mass fraction of hydrochloric acid is in the range of 36% to 38%. In this embodiment, the deposited titanium-based alloy is selectively etched for 5 hours using the above-mentioned etchant.
[0042] like Figure 2 As shown in the figure, during the selective etching process, the continuously generated porous structure and pores provide the etchant with a channel to the unetched portion of the lower layer of the alloy electrode, so that the etchant can selectively etch the lower layer of the alloy electrode. After the above process, the newly formed porous structure once again provides the etchant with a channel to the lower layer of the unetched alloy electrode. The same process is repeated, and finally other elements except titanium are removed by selective etching, thereby forming a porous electrode. Figure 3 Medium b and Figure 3 As shown in Figure c, in the process of forming the porous electrode, the aforementioned continuous conformal growth of each titanium-based alloy part is gradually separated into several porous titanium electrode structures independently existing on the photoresist layer and the substrate under the dual effects of the "T"-shaped double-layer photoresist and the continuously formed porous electrode. Among them, the porous titanium electrode structure located above the substrate is the high aspect ratio porous titanium electrode to be obtained in this embodiment. On the basis of the aforementioned steps, it is only necessary to remove the redundant porous titanium electrode structure located above the photoresist layer and the photoresist.
[0043] Therefore, after step 300, if Figure 2 As shown, step 400 is also included: a stripping step, in which a stripping agent is used to remove the first photoresist layer, the second photoresist layer and the inverted trapezoidal porous titanium electrode structure deposited on the second photoresist layer.
[0044] The stripping agent used is acetone. The first photoresist layer and the second photoresist layer can be removed by soaking in acetone for 30 minutes. At the same time, since the porous titanium electrode structure located above the photoresist layer has been completely separated from the porous titanium electrode structure above the substrate, the porous titanium electrode structure above the photoresist layer can be removed together.
[0045] like Figure 3 As shown in d, the high aspect ratio porous titanium electrode formed by the above method can have an aspect ratio of 0.1 to 0.4, and is 0.35 in this embodiment. The aspect ratio refers to the ratio between the depth of the porous titanium electrode structure and the distance between the two electrodes.
[0046] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.
Claims
1. A method for forming a porous titanium electrode with a high aspect ratio for a micro supercapacitor, characterized in that: include: A photolithography step, in which a first photoresist layer and a second photoresist layer that adhere to each other are formed on a substrate by photolithography, wherein a cross-sectional area of the first photoresist layer is smaller than a cross-sectional area of the second photoresist layer along a direction parallel to the substrate, the first photoresist layer is formed on the substrate, and the second photoresist layer is located on the first photoresist layer; A sputtering step, in which a titanium-based alloy is subjected to physical vapor deposition to form a titanium-based alloy electrode, wherein the mass percentage of titanium in the titanium-based alloy is 10% to 70%, and the titanium-based alloy is suitable for forming an inverted trapezoidal structure with the second photoresist layer as the bottom and a regular trapezoidal structure with the substrate as the bottom; An etching step, in which the titanium-based alloy electrode is selectively etched using an etchant to remove elements other than titanium in the titanium-based alloy electrode and gradually separate it into a plurality of porous titanium electrodes independently existing on the photoresist layer and the substrate.
2. The method for forming a micro-supercapacitor high aspect ratio porous titanium electrode according to claim 1, characterized in that: Also includes: A stripping step, in which the first photoresist layer, the second photoresist layer and the inverted trapezoidal porous titanium electrode structure deposited on the second photoresist layer are removed by using a stripping agent.
3. The method for forming a micro-supercapacitor high aspect ratio porous titanium electrode according to claim 1, characterized in that: The aspect ratio of the high aspect ratio porous titanium electrode is 0.1 to 0.
4.
4. The method for forming a micro-supercapacitor high aspect ratio porous titanium electrode according to claim 1, characterized in that: In the titanium-based alloy, the mass percentage of titanium is 30%, and the mass percentage of aluminum is 70%.
5. The method for forming a micro-supercapacitor high aspect ratio porous titanium electrode according to any one of claims 1 to 4, characterized in that: The first photoresist layer is made of AR-BR 5480, and the second photoresist layer is made of AZ601.
6. The method for forming a micro-supercapacitor high aspect ratio porous titanium electrode according to any one of claims 1 to 4, characterized in that: The sum of the thicknesses of the first photoresist layer and the second photoresist layer is 1.8 micrometers to 2.4 micrometers.
7. The method for forming a micro-supercapacitor high aspect ratio porous titanium electrode according to any one of claims 1 to 4, characterized in that: The thickness of the titanium-based alloy electrode is 3 micrometers to 12 micrometers.
8. The method for forming a micro-supercapacitor high aspect ratio porous titanium electrode according to any one of claims 1 to 4, characterized in that: The substrate comprises a silicon base and a silicon dioxide insulating layer.