Method of patterning an organic electrode

Abstract

Provided is a method for patterning an organic electrode. The method for patterning the organic electrode comprises: depositing a negative photoresist on an organic electrode layer to form a photoresist layer; patterning the photoresist layer to expose the organic electrode layer; etching the organic electrode layer to form a specific pattern of the organic electrode layer; and removing the photoresist layer to obtain the organic electrode. Thus, the prepared organic electrode has good electrical properties, and the method for patterning the organic electrode has good process stability.

Description

Technical Field

[0001] This application relates to the field of electrical component manufacturing, and more specifically to a method for patterning organic electrodes. Background Technology

[0002] Wearable flexible electronics (such as organic electrochemical transistors, flexible touch sensors, and artificial intelligence robots) have become the forefront of modern optoelectronics and sensor electronics research. As one of the most commonly used conductive polymers, PEDOT:PSS (poly3,4-ethylenedioxythiophene:polystyrene sulfonate) has become a more favored flexible electrode material than metal electrodes due to its optical transparency in the visible light range, tunable conductivity and work function, high flexibility, stretchability, and good biocompatibility. Despite the excellent electrode performance of PEDOT:PSS, the patterning etching technology for PEDOT:PSS films has limited its further application and development in the field of organic electrodes.

[0003] Currently, the patterning technology for organic electrodes PEDOT:PSS is mainly achieved through traditional photolithography. Generally, these processes fall into two categories: one utilizes patterned negative photoresist and lift-off techniques; the other uses a sacrificial layer material compatible with the properties of PEDOT:PSS as a mask in conjunction with reactive ion etching (RIE). After etching, the sacrificial layer can be removed by mechanical lift-off or wet etching.

[0004] The main process of negative photoresist and lift-off involves spin-coating negative photoresist onto a clean substrate, then exposing the PEDOT:PSS deposition area through UV exposure and development, followed by spin-coating of a PEDOT:PSS solution. After annealing and drying, excess photoresist is washed away with acetone. Since PEDOT:PSS requires high-temperature annealing for a certain time after spin-coating to form a film, and conventional photoresist cannot be completely removed after high-temperature and prolonged baking, residual insulating photoresist increases the contact resistance of the electrodes. Removing residual photoresist through ultrasonication or water baths reduces the electrode performance of the PEDOT:PSS film. Furthermore, shortening the annealing time of the PEDOT:PSS film can effectively reduce the amount of residual photoresist, but it also reduces the crystallinity of PEDOT:PSS, affecting the stability of the PEDOT:PSS film.

[0005] The process using a sacrificial mask typically involves spin-coating a PEDOT:PSS solution onto a clean substrate, annealing the PEDOT:PSS film, depositing a sacrificial layer (or protective layer) on top, etching away excess PEDOT:PSS using a suitable reactive ion etching process, and finally removing the protective layer using mechanical stripping or wet etching. Because most positive photoresists used in protective and etching processes have poor adhesion to the PEDOT:PSS surface, "resin bleed-off" is prone to occur during subsequent development, making it unsuitable to directly use positive photoresists as protective layers. Existing processes generally use materials such as bilayer parylene-C, aluminum (Al), silver (Ag), and silicon nitride (Si3N4) as protective layers. The process of using bilayer parylene as a protective layer is cumbersome, requiring more materials and equipment, and the subsequent removal of parylene by mechanical stripping limits the continuity of the PEDOT:PSS pattern. The process of using materials such as aluminum, silver, and silicon nitride as protective layers is relatively complex. The removal of the protective layer requires wet etching, and the etching solution may also damage the PEDOT:PSS film or substrate. Summary of the Invention

[0006] This application is made in view of the state of the prior art described above. The object of this application is to provide a method for patterning organic electrodes that overcomes at least one of the disadvantages described in the background art.

[0007] To achieve the above objectives, this application adopts the following technical solution.

[0008] This application provides a method for patterning an organic electrode, the method comprising: depositing a negative photoresist on an organic electrode layer to form a photoresist layer; patterning the photoresist layer to expose the organic electrode layer; etching the organic electrode layer to form a specific pattern on the organic electrode layer; and removing the photoresist layer to obtain the organic electrode.

[0009] In one alternative technical solution, the organic electrode layer comprises PEDOT:PSS.

[0010] In another alternative technical solution, a PEDOT:PSS solution is spin-coated and then annealed to form the organic electrode layer, wherein the thickness of the organic electrode layer is t. e Satisfying 600nm≤t e ≤800nm, annealing temperature T a Satisfying 120℃≤T a ≤150℃, annealing time L a Satisfying 30min≤L a ≤90min.

[0011] In another alternative technical solution, the organic electrode layer is deposited on the stabilizing layer to promote the crosslinking of the organic electrode layer.

[0012] In another alternative technical solution, a solution of 3-glycidyl etheroxypropyltrimethoxysilane is spin-coated to form the stable layer.

[0013] In another alternative technical solution, the stabilizing layer is deposited on a substrate, the substrate comprising at least one of silicon, glass, polyimide, and polyethylene terephthalate.

[0014] In another alternative technical solution, the negative photoresist comprises propylene glycol methyl ether acetate.

[0015] In another alternative technical solution, patterning the photoresist layer includes pre-baking, exposure, post-baking, and development, wherein the pre-baking temperature T pre Satisfying 100℃≤T pre ≤120℃, the exposure dose W e Satisfying 40mJ≤W e ≤60mJ, the post-drying temperature T post Satisfying 100℃≤T post ≤120℃, the development time L d Satisfying 60s≤L d ≤80s.

[0016] In another alternative technical solution, the etching is reactive ion etching, and the etching gas includes oxygen and sulfur hexafluoride, wherein the volumetric flow rate of the oxygen is Q. o Satisfying 90sccm≤Q o The volumetric flow rate Q of the sulfur hexafluoride is ≤110 sccm. sh Satisfying 3sccm≤Q sh ≤7sccm, the etching power P e Satisfying 80W≤P e ≤120W, the etching duration L e Satisfying 100s≤L e ≤140s.

[0017] In another alternative technical solution, removing the photoresist layer includes immersing the photoresist layer in an organic solvent.

[0018] By employing the above technical solution, the photoresist layer can be deposited on the organic electrode layer after it has been formed, thus avoiding the problem of difficult removal of negative photoresist. This prevents residual negative photoresist from increasing the contact resistance of the organic electrode and improving its performance. Furthermore, using negative photoresist to form the photoresist layer allows it to easily adhere to the organic electrode layer. Therefore, during the patterning of the organic electrode, the photoresist layer is less likely to accidentally detach from the organic electrode layer (resin detachment phenomenon), ensuring process stability. Attached Figure Description

[0019] Figure 1 A schematic diagram of a method for patterning organic electrodes according to a first embodiment of this application is shown.

[0020] Figure 2 It shows Figure 1 A schematic diagram of the patterns that can be formed by organic electrodes.

[0021] Figure 3 A schematic diagram of an organic electrochemical transistor according to a second embodiment of this application is shown.

[0022] Figure 4 It shows Figure 3 A schematic diagram of the measurement of an organic electrochemical transistor.

[0023] Figure 5 It shows Figure 3 The output characteristic curve of the organic electrochemical transistor in the image.

[0024] Figure 6 It shows Figure 3 Stability curves of organic electrochemical transistors in [the image / image].

[0025] Explanation of reference numerals in the attached figures

[0026] 1. Base;

[0027] 2. Organic electrode layer; 21 channels;

[0028] 3. Photoresist layer;

[0029] 4. Source layer;

[0030] 5. Drain layer;

[0031] 6 encapsulation layers; 6a opening;

[0032] 7. Electrolytes;

[0033] 8. Gate. Detailed Implementation

[0034] Exemplary embodiments of this application are described below with reference to the accompanying drawings. It should be understood that these specific descriptions are for teaching those skilled in the art how to implement this application only, and are not intended to exhaust all possible methods of this application, nor to limit the scope of this application.

[0035] In this application, unless otherwise specified, "organic electrode" refers to a device made using organic materials or a combination of organic materials and other materials.

[0036] Figures 1 to 2 A first embodiment according to this application is shown.

[0037] Reference Figure 1 This application provides a method for patterning organic electrodes, which may include:

[0038] A solution of 3-GOPS (3-glycidoxypropyltrimethoxysilane) was spin-coated onto substrate 1 to form a stable layer. Figure 1 (not shown in the image);

[0039] Spin-coat the PEDOT:PSS solution onto the stabilizing layer;

[0040] Anneal the PEDOT:PSS solution to form organic electrode layer 2, such as Figure 1 As shown in (a);

[0041] Negative photoresist is spin-coated onto organic electrode layer 2 to form photoresist layer 3;

[0042] The patterned photoresist layer 3 exposes a portion of the organic electrode layer 2, such as... Figure 1 As shown in (b);

[0043] Etching the organic electrode layer 2 to pattern the organic electrode layer 2, such as... Figure 1 As shown in (c);

[0044] Photoresist layer 3 is removed by immersing it in an organic solvent, such as... Figure 1 As shown in (d).

[0045] Using the above method, the photoresist layer 3 can be deposited on the organic electrode layer 2 after annealing in the PEDOT:PSS solution. The annealing process does not affect the photoresist layer 3, thus avoiding the problem of difficult removal of negative photoresist after prolonged baking. This prevents residual negative photoresist from increasing the contact resistance of the organic electrode and improving its performance. Simultaneously, the PEDOT:PSS solution can have a longer annealing time without being limited by the photoresist layer 3, thereby improving the crystallinity of PEDOT:PSS and ensuring the stability of the organic electrode. Secondly, using negative photoresist to form the photoresist layer 3 allows it to easily adhere to the organic electrode layer 2. This prevents the photoresist layer 3 from accidentally detaching from the organic electrode layer 2 during the patterning of the organic electrode (preventing "resin detachment"), ensuring process stability. Furthermore, the stabilizing layer promotes cross-linking of the organic electrode layer 2, making it more stable in aqueous solutions.

[0046] Reference Figure 2 By employing the above method, the organic electrode layer 2 can form various patterns. Specifically, the patterns can be circular, square, or striped. Of course, the patterns formed by the organic electrode layer 2 can be any combination of these simple shapes or more complex patterns. The precision of the pattern can be at least 10 μm.

[0047] By setting the parameters of the spin coater, the stabilizing layer, organic electrode layer 2, and photoresist layer 3 can have a certain thickness. Specifically, when spin-coating the 3-GOPS solution, the spin-coating speed can be, for example, 4000 rpm, and the spin-coating time can be 40 seconds. When spin-coating the PEDOT:PSS solution, the spin-coating speed can be 2000 rpm to 4000 rpm, for example, 2500 rpm, and the spin-coating time can be, for example, 40 seconds. Preferably, the thickness of the organic electrode layer 2 can be 600 nm to 800 nm. When spin-coating the negative photoresist, the spin-coating speed can be, for example, 3000 rpm, and the spin-coating time can be, for example, 40 seconds.

[0048] Annealing allows the water in the PEDOT:PSS solution to evaporate, thus causing PEDOT:PSS to crystallize. To obtain a stable organic electrode layer 2, the annealing temperature can be between 120°C and 150°C, for example, 120°C, and the annealing time can be between 30 min and 90 min, for example, 60 min. After annealing, the organic electrode layer 2 can be allowed to cool naturally to room temperature.

[0049] The negative photoresist can be AZ nLOF 2070 type photoresist, whose main component is propylene glycol methyl ether acetate. The photoresist layer 3 can be patterned using conventional ultraviolet lithography. Specifically, the photoresist layer 3 can be patterned by pre-baking, exposure, post-baking, and development. Specifically, the pre-baking and post-baking temperatures can be from 100°C to 120°C, for example, 110°C. The exposure dose can be from 40 mJ (millijoules) to 60 mJ, for example, 50 mJ. The development time can be from 60 s to 80 s, for example, 70 s. After development, each layer can be dried using nitrogen gas. Conventional ultraviolet lithography technology is mature, and its use is beneficial for the mass production of organic electrodes.

[0050] The organic electrode layer 2 can be reactively etched using a mixture of oxygen and sulfur hexafluoride. Specifically, the oxygen volumetric flow rate can be from 90 sccm (mL / min at standard conditions), to 110 sccm, for example, 100 sccm. The sulfur hexafluoride volumetric flow rate can be from 3 sccm to 7 sccm, for example, 5 sccm. The etching power can be from 80 W to 120 W, for example, 100 W. The etching duration can be from 100 s to 140 s, for example, 120 s.

[0051] The organic solvent can be acetone. Specifically, each layer can be immersed in acetone for 5 to 10 minutes. Compared with methods such as heating or ultrasonication to remove the photoresist layer 3, using acetone to remove the photoresist layer 3 will not damage the electrical properties of the organic electrode layer 2. After immersion, each layer can be rinsed sequentially with isopropanol and deionized water, and then dried with nitrogen.

[0052] Substrate 1 can be a silicon wafer. Before performing the above method, the silicon wafer can be cleaned to ensure it is clean. Specifically, the silicon wafer can be cleaned sequentially with acetone, isopropanol, and deionized water. Furthermore, the silicon wafer can have a specific size; for example, it can be a 1cm x 1cm square wafer.

[0053] Figures 3 to 6 A second embodiment according to this application is shown.

[0054] Reference Figure 3 Methods for obtaining organic electrochemical transistors may include:

[0055] A source layer 4 and a drain layer 5 are deposited on substrate 1;

[0056] The patterned organic electrode layer 2 is formed using the method in the first embodiment, such that at least a portion of the organic electrode layer 2 is formed as a channel 21;

[0057] Each layer is encapsulated using a packaging layer 6, with only the channel 21 exposed to the outside of the packaging layer 6. The source layer 4 and the drain layer 5 can be electrically connected to the outside of the packaging layer 6 through the test terminal.

[0058] In this way, an organic electrochemical transistor is obtained, with organic electrode layer 2 as channel 21, source layer 4 as source, and drain layer 5 as drain.

[0059] To obtain a flexible organic electrochemical transistor, substrate 1 may include a rigid body and an elastomer. The rigid body may be a silicon wafer, and the elastomer may be polyimide (PI). Specifically, the polyimide can be attached to the silicon wafer, and the source layer 4 and drain layer 5 can be deposited on the polyimide. After packaging, the silicon wafer and polyimide can be separated to remove the silicon wafer. In this way, the rigid silicon wafer can fix the elastic polyimide for easy handling, and the elastic polyimide enables the organic electrochemical transistor to be flexible.

[0060] The source layer 4 can be a chromium (Cr) layer with a thickness of 5 nm. The drain layer 5 can be a gold (Au) layer with a thickness of 100 nm.

[0061] The encapsulation layer 6 may include photoresist. Specifically, the photoresist may be SU-8 3005 type photoresist. The encapsulation layer 6 may be patterned to form an opening 6a, allowing the channel 21 to be exposed from the encapsulation layer 6 through the opening 6a.

[0062] Reference Figure 4 An external electrode can be used as the gate 8 to measure the electrical characteristics of the organic electrochemical transistor. The gate 8 is connected to the channel 21 via the electrolyte 7. The gate 8 can be a silver electrode or a silver chloride (AgCl) electrode. The electrolyte 7 can be a sodium chloride (NaCl) solution with a concentration of 0.1 M (mol / L). The electrolyte 7 is able to contact the channel 21 only through the opening 6a, without contacting the source layer 4 and the drain layer 5. During measurement, an external power supply can be connected to the test terminal and the gate 8, allowing the external power supply to apply a gate voltage V to the organic electrochemical transistor. g and drain voltage V d .

[0063] Measurement results as follows Figure 5 and Figure 6 shown. Specifically, Figure 5 The output characteristic curves of the organic electrochemical transistor are shown, reflecting the organic electrochemical transistor at different gate voltages V. g Lower drain current I d With drain voltage V d The relationship between them. Figure 5It can be seen that the output characteristic curve has a saturation region, a cutoff region, and an amplification region, and the prepared organic electrochemical transistor can work normally. Figure 6 The stability curves of the organic electrochemical transistor are shown, reflecting the stability of the organic electrochemical transistor under the same drain voltage V. d The output characteristic curves were obtained from multiple measurements. The output characteristic curves from each measurement largely overlapped, indicating that the fabricated organic electrochemical transistor exhibited good stability.

[0064] This application has at least the following advantages:

[0065] (i) The photoresist layer 3 can be deposited on the organic electrode layer 2 after annealing in the PEDOT:PSS solution. The annealing process does not affect the photoresist layer 3, thus avoiding the problem of negative photoresist being difficult to remove after long-term baking. There will be no residual negative photoresist increasing the contact resistance of the organic electrode, thereby improving the performance of the organic electrode.

[0066] (ii) The PEDOT:PSS solution can have a longer annealing time without being limited by the photoresist layer 3, thereby improving the crystallinity of PEDOT:PSS and ensuring the stability of the organic electrode.

[0067] (iii) A negative photoresist is used to form a photoresist layer 3, which easily adheres to the organic electrode layer 2. During the patterning of the organic electrode, the photoresist layer 3 is less likely to accidentally detach from the organic electrode layer 2 (resin detachment phenomenon), ensuring the stability of the process.

[0068] (iv) The stabilizing layer can promote the cross-linking of the organic electrode layer 2, making the organic electrode layer 2 more stable in aqueous solution.

[0069] It should be understood that the above embodiments are merely exemplary and are not intended to limit this application. Those skilled in the art can make various modifications and changes to the above embodiments under the teachings of this application without departing from the scope of this application.

[0070] It should be understood that the substrate is not limited to silicon wafers and polyimide, and can be made of any possible material known to those skilled in the art. For example, the substrate can also be glass or polyethylene terephthalate.

[0071] It should be understood that the organic electrode layer 2 is not limited to PEDOT:PSS, and may include any possible organic material or combination of organic and non-organic materials known to those skilled in the art. For example, the organic electrode layer 2 may also include one or more of polyacetylene (PA), polythiophene (PT), polypyrrole (PPy), polyphenylene oxyether (PPO), and polyaniline (PANi).

[0072] It should be understood that the stabilizing layer is not limited to 3-GOPS, and may include any material known to those skilled in the art that facilitates the crosslinking of the organic electrode layer 2. The stabilizing layer is not mandatory, and the organic electrode layer 2 may also be deposited directly on the substrate 1.

Claims

1. A method for patterning organic electrodes, characterized in that, include: Spin-coating a solution of 3-glycidyl etheroxypropyltrimethoxysilane to form a stable layer. An organic electrode layer (2) is deposited on the stabilizing layer to promote the crosslinking of the organic electrode layer (2). A negative photoresist is deposited on the organic electrode layer (2) to form a photoresist layer (3); Pattern the photoresist layer (3) to expose the organic electrode layer (2); The organic electrode layer (2) is etched to form a specific pattern on the organic electrode layer (2); Remove the photoresist layer (3) to obtain the organic electrode.

2. The method for patterning organic electrodes according to claim 1, characterized in that, The organic electrode layer (2) includes PEDOT:PSS.

3. The method for patterning organic electrodes according to claim 2, characterized in that, A PEDOT:PSS solution is spin-coated and annealed to form the organic electrode layer (2), the thickness of which is t. e Satisfying 600 nm≤t e ≤800 nm, annealing temperature T a Satisfying 120℃≤T a ≤150℃, annealing time L a Satisfying 30 min≤L a ≤90 min.

4. The method for patterning organic electrodes according to claim 1, characterized in that, The stabilizing layer is deposited on a substrate (1), the substrate (1) comprising at least one of silicon, glass, polyimide and polyethylene terephthalate.

5. The method for patterning organic electrodes according to any one of claims 1 to 4, characterized in that, The negative photoresist includes propylene glycol methyl ether acetate.

6. The method for patterning organic electrodes according to any one of claims 1 to 4, characterized in that, Patterning the photoresist layer (3) includes pre-baking, exposure, post-baking, and development, wherein the pre-baking temperature T pre Satisfying 100℃≤T pre ≤120℃, the exposure dose W e Satisfying 40 mJ ≤ W e ≤60 mJ, the post-drying temperature T post Satisfying 100℃≤T post ≤120℃, the development time L d Satisfying 60 s≤L d ≤80 s.

7. The method for patterning organic electrodes according to any one of claims 1 to 4, characterized in that, The etching is reactive ion etching, and the etching gas includes oxygen and sulfur hexafluoride, with a volumetric flow rate Q of oxygen. o Satisfying 90sccm≤Q o ≤110 sccm, the volumetric flow rate Q of the sulfur hexafluoride sh Satisfying 3 sccm≤Q sh ≤7 sccm, the etching power P e Satisfying 80 W≤P e ≤120 W, the etching duration L e Satisfying 100 s≤L e ≤140 s.

8. The method for patterning organic electrodes according to any one of claims 1 to 4, characterized in that, Removing the photoresist layer (3) includes immersing the photoresist layer (3) in an organic solvent.

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