Full-mask photoetching-free cluster film memristor array and preparation method thereof

Abstract

The invention relates to the technical field of cluster film devices, in particular to a full-mask photoetching-free cluster film memristor array and a preparation method thereof. The array comprises bottom electrodes and top electrodes, the number of the bottom electrodes and the number of the top electrodes are the same as the number of device arrays, the bottom electrode array is tightly attached to the surface of a substrate through a mask I and is formed through the EBE technology, and N through holes are formed in the mask I; covering the through holes of the mask I with N masks II, and forming an insulating dielectric layer by using an ALD technology; the mask III replaces the mask II to cover the insulating dielectric layer, a top electrode array is deposited on the insulating dielectric layer through the EBE technology, and N through holes are formed in the mask III; self-assembling a cluster film with a memristor characteristic to form a cluster film functional layer; and selecting a functional metal electrode to connect the cluster film functional layer and the top electrode so as to prepare the cluster film memristor array. According to the method, the dependence on high-vacuum and high-energy-consumption equipment is completely eliminated through a pure physical mask method.

Description

Technical Field

[0001] This invention relates to the field of cluster film device technology, specifically to a full-mask, photolithography-free cluster film memristor array and its fabrication method. Background Technology

[0002] Clustered membrane memristors, due to their unique quantum size effect and controllable conductivity channel evolution, have shown great application potential in non-volatile logic operations and neuromorphic computing. They can serve as the core basic device for future information storage and computing integration computing models and non-von Neumann computing architectures.

[0003] Currently, cluster film memristors are at a critical stage of transitioning from laboratory verification to commercial applications. A prerequisite for realizing their high-performance computing capabilities is the fabrication of high-density device arrays. However, existing cluster film array fabrication processes heavily rely on high-precision patterning techniques such as electron beam lithography (EBL) or ultraviolet lithography (EUV). While these techniques offer high resolution, they also have significant limitations in practical research and production. First, the process costs and barriers to entry are extremely high; lithography equipment (such as lithography machines and coating / developing systems) is extremely expensive and maintenance costs are high, resulting in huge upfront R&D investment. Second, the process is complex and time-consuming: traditional lithography processes involve multiple coating, pre-baking, exposure, development, and etching steps, leading to long fabrication cycles.

[0004] Therefore, developing a method for fabricating cluster film memristor arrays that does not require photolithography, has a simplified process, is low in cost, and has high versatility is of great practical significance and technical value for accelerating the rapid verification of the performance of cluster film devices and promoting their industrialization. Summary of the Invention

[0005] This invention provides a method for fabricating a full-mask, photolithography-free cluster film memristor array, which solves the problems of high dependence on high-precision patterning technologies such as EBL in the fabrication of existing cluster film memristor arrays, resulting in complex process flow, high R&D costs, and long fabrication cycle.

[0006] The present invention discloses a fully mask-based, photolithography-free cluster film memristor array, wherein each cluster film memristor is a two-terminal device. The cluster film memristor array includes a number of bottom electrodes and a number of top electrodes equal to the number of device arrays. The bottom electrode array is formed by depositing bottom metal electrodes using a mask I tightly attached to the substrate surface through an EBE process. The mask I has N through-holes corresponding to the substrate. N masks II cover the N through-holes of the bottom electrode array, and an insulating dielectric layer is deposited using an ALD process. Mask III replaces mask II and covers the insulating dielectric layer, and the top electrode array is deposited at specific positions on the insulating dielectric layer again using an EBE process. The mask III has N through-holes. On the sample with the prepared top electrode array, a cluster film with memristor properties is self-assembled at room temperature, so that cluster molecules form a cluster film functional layer on the sample. A functional metal electrode with memristor properties that is bonded to the cluster film is selected and connected to the cluster film functional layer and the top electrode to form the cluster film memristor array.

[0007] Preferably, the functional metal is a liquid metal, which is fixed by polyimide tape and serves as a functional metal electrode connecting the top electrode and the cluster film functional layer.

[0008] Preferably, the N through holes of the mask III do not overlap with the N through holes provided on the corresponding substrate of the mask I.

[0009] The method for fabricating a cluster film memristor array without photolithography using a full mask as described in this invention includes the following steps: (1) Select a substrate with a conductive layer on its surface, place mask I tightly on the surface of the substrate, and deposit the bottom metal electrode through EBE process to form a bottom electrode array; the mask I has N through holes corresponding to the substrate; (2) Cover the N through holes of the bottom electrode array with N mask II, and deposit a dense insulating dielectric layer using ALD technology. The mask II divides the substrate into functional regions by patterning the insulating dielectric layer, ensuring that the cluster film deposited later only contacts the functional electrode within the preset window. (3) Cover the insulating dielectric layer with mask III, and deposit the top electrode array at a specific position on the insulating dielectric layer again through EBE process; the mask III is provided with N through holes, which do not overlap with the N through holes provided on the substrate of mask I; (4) On the sample with the prepared top electrode array, a cluster film with memristor properties is self-assembled by spin coating, drop coating or solution deposition, and the cluster molecules form a cluster film functional layer on the sample at room temperature. (5) Select a functional metal electrode that has memristor properties that is combined with the cluster film, and connect the cluster film and the top electrode to prepare a cluster film memristor array; wherein the functional metal is a liquid metal, and the liquid metal is fixed by polyimide tape as a functional metal electrode connecting the top electrode and the cluster film.

[0010] Preferably, the liquid metal is a gallium-indium alloy.

[0011] Preferably, the insulating dielectric layer is an HfO2 insulating layer.

[0012] Preferably, the through-holes in the mask are square through-holes.

[0013] Preferably, the substrate is glass with an indium tin oxide (ITO) conductive layer with a surface thickness of 200±50 nm.

[0014] Preferably, the substrate is a rigid substrate, a flexible substrate, or a non-flat substrate.

[0015] Preferably, the photomask is made of a high-temperature rigid material.

[0016] Preferably, the bottom electrode and the top electrode are made of any conventional electrode metal material.

[0017] Preferably, the EBE process is performed at a vacuum level of 10. -5 Deposition was carried out at a rate of 0.5 Å / s under the conditions of Pa and substrate temperature of 30 °C.

[0018] Preferably, the ALD technology is performed at 90 °C with a growth rate of 0.18 nm / Cycle.

[0019] This invention achieves efficient fabrication of cluster film memristor arrays through a purely physical masking method, eliminating the need for photoresist and chemical development processes. It simplifies the process flow, eliminating the cumbersome steps of traditional photolithography such as coating, pre-baking, exposure, development, fixing, and stripping, enabling integrated physical fabrication from substrate preparation to array formation. This lowers the R&D and entry barriers, reducing reliance on expensive photolithography equipment and significantly reducing hardware and consumable costs for early-stage device verification. Furthermore, it enhances fabrication flexibility, as the method is applicable not only to conventional rigid substrates but also to flexible substrates, enabling rapid template switching and verification for different array structure requirements. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the mask dimensions designed in the embodiments of the present invention; Figure 2 This is a schematic diagram of the clustered film memristor array in the embodiment of the present invention; Figure 3The clustered film memristor array measured in this invention IV Line graph; Figure 4 This is a transient response diagram of the clustered film memristor array measured in this invention; Figure 5 for Figure 4 A magnified view of the area within the blue box. Detailed Implementation

[0021] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention.

[0022] The fully masked, photolithography-free clustered film memristor array of this invention comprises a single clustered film memristor that is a two-terminal device. The clustered film memristor array includes the same number of bottom electrodes and top electrodes as the number of device arrays. The bottom electrodes and top electrodes can be made of any conventional electrode metal material, such as gold (Au) or platinum (Pt).

[0023] A high-temperature resistant hard mask I is attached tightly to the substrate surface, and a bottom metal electrode is deposited using an electron beam evaporation deposition (EBE) process to form a bottom electrode array; the mask I has N through holes corresponding to the substrate. A high-temperature resistant hard mask II is placed over the bottom electrode array, and a dense insulating dielectric layer, such as 20 nm HfO2, is deposited using atomic layer deposition (ALD) technology. The N mask IIs are respectively covered on the through-hole array of the prepared bottom electrode sample. The mask IIs are used to modularly divide the substrate into functional regions by patterning the insulating dielectric layer, ensuring that the subsequently deposited cluster film only contacts the functional electrode within a preset window. A high-temperature resistant hard mask III replaces mask II and covers the insulating dielectric layer. Then, an electron beam evaporation deposition (EBE) process is used to deposit a top electrode array at specific locations on the insulating dielectric layer. Mask III has N through holes to form an array, and these N through holes do not overlap with the N through holes on the substrate of mask I. Specifically, the insulating dielectric layer is an HfO2 insulating layer. On a sample with a prepared top electrode array, a cluster film with memristor properties is self-assembled by spin coating, drop coating or solution deposition to form a cluster film functional layer. The cluster film functional layer described in this invention is assembled after the sample is prepared. This post-assembly method can avoid cluster failure caused by electrode evaporation and improve interface quality and device repeatability. A functional metal electrode with memristor properties is selected and connected to the cluster film functional layer and the top electrode. The functional metal electrode is a liquid metal, such as gallium indium alloy (EGaIn) or mercury (Hg). Specifically, the liquid metal gallium indium alloy (EGaIn) is fixed with polyimide (PI) tape as a functional electrode to connect the top electrode of the four devices to the cluster film functional layer, so as to prepare and form a cluster film memristor array.

[0024] The device fabricated in this invention is suitable for applications requiring liquid metals, such as EGaIn, as the functional material for contacting the metal. Since liquid metals cannot be fabricated using traditional processes such as electron beam evaporation, the assembly method of fixing EGaIn with polyimide (PI) tape to the functional metal electrodes completely eliminates the reliance on high-vacuum, high-energy-consumption equipment. The fabricated cluster film memristor array... IV The curve exhibits memristor characteristics, i.e., hysteresis; the prepared cluster film memristor array shows transient current response and significant channel resistance changes under pulsed voltage excitation. This invention can be used on rigid substrates, flexible substrates, or non-planar substrates as substrates.

[0025] Example 1

[0026] The method for fabricating a clustered film memristor array according to the present invention includes the following steps: 1) Select a glass substrate with an indium tin oxide (ITO) conductive layer with a thickness of 200±50 nm as the substrate. The substrate has a size of 10×10×1.1 mm. It is ultrasonically cleaned in sequence with deionized water, ethanol, acetone and isopropanol to remove organic contaminants on the surface. Then it is dried with a nitrogen gun for later use. 2) A custom-made SUS304 stainless steel high-temperature resistant metal photomask I (10×10×0.4 mm) is used. This photomask has 1×1 mm square through-holes at 1.5 mm positions at the four corners of the corresponding substrate. Figure 1 As shown in the left figure; 3) Attach the photomask to the ITO substrate, place the assembly in the EBE (Environmentally Protected Array), and maintain a vacuum of 10... -5 Under the conditions of Pa and substrate temperature of 30℃, 10 nm thick Cr and 50 nm thick Au were deposited at a rate of 0.5 Å / s to form four bottom electrode arrays. 4) Four miniature high-temperature resistant metal mask II (4×4×0.4 mm in size) are used to cover the four vertices of the prepared bottom electrode sample to define the contact windows between the subsequent functional layers and the electrodes, thereby realizing the array partitioning of the device; 5) Using ALD technology, tetramethylaminohafnium (C8H) 24Using HfN4 and water as precursors, a 20 nm thick HfO2 insulating layer was deposited at 90 °C with a growth rate of 0.18 nm / Cycle. 6) Replace mask II with mask III, which is designed to pattern the top electrode (10×10×0.4 mm). It patterns 1×1 mm square apertures at positions 2 mm from the parallel edges and 5 mm from the vertical edges on all four sides. Figure 1 As shown in the right figure; 7) Repeat the EBE deposition process to deposit a 10 nm thick Cr and a 50 nm thick Au top electrode at specific locations on the HfO2 insulating layer, with the same evaporation parameters as the bottom electrode. 8) Immerse the prepared sample in a molecular solution with memristor properties and perform a self-assembly process at room temperature for 48 hours to form a cluster membrane functional layer on the sample. After removal, allow it to air dry naturally in a cleanroom. 9) The clustered film memristor array prepared in this invention exhibits obvious bipolar resistive switching behavior. For example... Figure 3 As shown, the specific physical process of the memristor characteristic curve is as follows: During the negative voltage scan from stage IV to stage I, the device undergoes a set operation. Stage I involves scanning the voltage from 0 V to the negative peak value of -1 V. As the negative bias increases, the electric field drives the formation of conductive channels within the cluster film functional layer, and the device transitions from the initial high-resistivity state (HRS) to the low-resistivity state (LRS), with the current rapidly increasing. Subsequently, in stage II, the voltage increases from the negative peak value through zero to the positive direction. Due to the stability of the conductive channels formed in stage I, the device exhibits resistance-maintaining characteristics, remaining in the low-resistivity state (LRS), thus producing a significant hysteresis phenomenon. Immediately following, during the positive scan from stage II to stage III, when the voltage reaches a certain threshold, the device undergoes a reset operation, the conductive channels break, and the device transitions back from the low-resistivity state (LRS) to the high-resistivity state (HRS), with the current significantly decreasing. Finally, in stage IV, the device returns to the high-resistivity state (HRS) and prepares to enter the next cycle. In this embodiment, a cyclic continuous scanning voltage of -1V to 1V is applied between the bottom and top electrodes using a lock-in amplifier. Experimental results show that after 12 consecutive scans, the curves have extremely high overlap, proving that the clustered film memristor array prepared using the full-mask process of this invention has excellent cyclic stability and reproducibility; at a read voltage of 0.1V, the theoretical on / off ratio can reach 700%.

[0027] 10) Use a pulse signal generator to apply a waveform with an amplitude of ±1 V and a pulse width of 100 μs (0.001s). For example... Figure 4 and Figure 5As shown, the clustered film memristor array exhibits a clear transient current response under pulse excitation. After the pulse is removed, the resistance state changes rapidly and remains stable at a read voltage of 0.1 V, demonstrating that the clustered film memristor array prepared in this invention possesses good non-volatile storage and multi-state switching capabilities.

[0028] The memristor array and its fabrication method provided in this application have been described in detail above. Specific examples have been used to illustrate the principles and implementation methods of this application. The descriptions of the embodiments above are only for the purpose of helping to understand the method and core ideas of this application. It should be noted that those skilled in the art can make several improvements and modifications to this application without departing from the principles of this application, and these improvements and modifications also fall within the protection scope of the claims of this application.

Claims

1. A fully masked, photolithography-free clustered film memristor array, wherein each clustered film memristor is a two-terminal device, characterized in that, The clustered film memristor array includes the same number of bottom electrodes and top electrodes as the number of device arrays. The bottom electrode array is formed by depositing bottom metal electrodes using a mask I that is closely attached to the substrate surface and using an EBE process. The mask I has N through holes corresponding to the substrate. N mask IIs cover the N through holes of the bottom electrode array and form an insulating dielectric layer using ALD technology. Mask III replaces mask II and covers the insulating dielectric layer. The top electrode array is deposited at a specific position on the insulating dielectric layer again through the EBE process. Mask III has N through holes. On the sample with the prepared top electrode array, a cluster film with memristor properties is self-assembled at room temperature, so that the cluster molecules form a cluster film functional layer on the sample. A functional metal electrode with memristor properties that is combined with the cluster film is selected and connected to the functional layer of the cluster film and the top electrode to prepare a cluster film memristor array.

2. The all-mask, photolithography-free clustered film memristor array according to claim 1, characterized in that, The functional metal is a liquid metal, which is fixed with polyimide tape and serves as a functional metal electrode connecting the top electrode and the cluster film functional layer.

3. The all-mask, photolithography-free clustered film memristor array according to claim 1, characterized in that, The N through holes of the mask plate III do not overlap with the N through holes on the corresponding substrate of the mask plate I.

4. A method for fabricating a cluster film memristor array using a full-mask, photolithography-free process, characterized in that, Includes the following steps: (1) Select a substrate with a conductive layer on its surface, place mask I tightly on the surface of the substrate, and deposit the bottom metal electrode through EBE process to form a bottom electrode array; the mask I has N through holes corresponding to the substrate; (2) Cover the N through holes of the bottom electrode array with N mask II, and deposit a dense insulating dielectric layer using ALD technology. The mask II divides the substrate into functional regions by patterning the insulating dielectric layer, ensuring that the cluster film deposited later only contacts the functional electrode within the preset window. (3) Replace mask II with mask III and cover the insulating dielectric layer. Then, deposit the top electrode array at a specific position on the insulating dielectric layer again through the EBE process. Mask III has N through holes, which do not overlap with the N through holes on the substrate of mask I. (4) On the sample with the prepared top electrode array, a cluster film with memristor properties is self-assembled by spin coating, drop coating or solution deposition, and the cluster molecules form a cluster film functional layer on the sample at room temperature. (5) Select a functional metal electrode that has memristor properties that is combined with the cluster film, and connect the functional layer of the cluster film to the top electrode to prepare and form a cluster film memristor array. The functional metal is a liquid metal, which is fixed by polyimide tape and serves as a functional metal electrode connecting the top electrode and the cluster film.

5. The method for fabricating a clustered film memristor array according to claim 4, characterized in that, The liquid metal is a gallium-indium alloy or mercury.

6. The method for fabricating a clustered film memristor array according to claim 4, characterized in that, The insulating dielectric layer is an HfO2 insulating layer.

7. The method for fabricating a clustered film memristor array according to claim 4, characterized in that, The through-holes in the mask are square through-holes.

8. The method for fabricating a clustered film memristor array according to claim 4, characterized in that, The substrate is glass with an indium tin oxide (ITO) conductive layer with a thickness of 200±50 nm on its surface.

9. The method for fabricating a clustered film memristor array according to claim 4, characterized in that, The substrate is a rigid substrate, a flexible substrate, or a non-flat substrate.

10. The method for fabricating a clustered film memristor array according to claim 4, characterized in that, The photomask is made of a high-temperature rigid material.

11. The method for fabricating a clustered film memristor array according to claim 4, characterized in that, The bottom and top electrodes are made of any conventional electrode metal material.

12. The method for fabricating a clustered film memristor array according to claim 4, characterized in that, The EBE process is performed at a vacuum level of 10. -5 Deposition was carried out at a rate of 0.5 Å / s under the conditions of Pa and substrate temperature of 30 °C.

13. The method for fabricating a clustered film memristor array according to claim 4, characterized in that, The ALD technology is used to deposit material at a growth rate of 0.18 nm / Cycle at 90 °C.

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