Alscn-based optical-ferroelectric synapse device and preparation method
By designing an AlScN-based opto-ferroelectric synaptic device, utilizing its polarization and photoresponse characteristics, the speed bottleneck and power consumption problems of traditional computing architectures are solved, enabling accurate writing, memorization, and lossless reading of information, with a simple device structure.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- CHANGCHUN INST OF OPTICS FINE MECHANICS & PHYSICS CHINESE ACAD OF SCI
- Filing Date
- 2023-02-17
- Publication Date
- 2026-05-15
AI Technical Summary
Traditional von Neumann computing architecture suffers from severe speed bottlenecks and power waste when processing massive amounts of unstructured data. Existing opto-ferroelectric synaptic devices have room for performance improvement. AlScN materials have high compatibility and strong residual polarization, making them suitable for artificial synaptic devices.
Design an AlScN-based opto-ferroelectric synapse device, comprising a substrate, a bottom electrode, an AlScN ferroelectric layer, and a top electrode arranged from bottom to top. The polarization direction of the AlScN ferroelectric layer is controlled by an external voltage, and its residual polarization characteristics are used to realize information writing and memory, and lossless optical reading is performed under zero bias voltage.
It achieves accurate writing and memorization of information, and lossless reading under zero bias voltage. The device has a simple structure and significantly improved performance.
Smart Images
Figure CN115996624B_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of semiconductor technology, and in particular to an AlScN-based opto-ferroelectric synapse device and its fabrication method. Background Technology
[0002] With the advent of the Internet of Things, cloud computing, and big data era, the traditional von Neumann computing architecture, which separates computing and storage units, is unable to handle the in-depth analysis and processing of massive amounts of unstructured data, facing speed bottlenecks and wasted power. In contrast, the human brain transmits and processes information through synapses, consuming only about 20 watts and achieving advanced intelligence far exceeding that of computers at low frequencies of tens of hertz, making it a model of high-performance, low-power computing hardware in nature. Therefore, developing artificial synaptic devices with the required characteristics has become a current research hotspot.
[0003] Ferroelectric materials possess polarization characteristics that can be controlled by an applied electric field, enabling the writing or editing of information via electrical pulses; their residual polarization characteristics can be used for information storage and computation; furthermore, based on the light absorption characteristics of ferroelectric materials, memory information can be extracted non-destructively by reading photocurrents, making them a popular material for fabricating artificial synaptic devices.
[0004] Compared to traditional ferroelectric materials, AlScN, as a novel nitride ferroelectric material, exhibits higher compatibility with current CMOS processes, attracting widespread attention in recent years. AlScN's remanent polarization intensity is 3-5 times that of traditional oxide ferroelectric materials; this strong remanent polarization characteristic can significantly enhance the stability and accuracy of information storage. Furthermore, AlScN possesses a large bandgap, with its photoresponse located in the solar-blind ultraviolet band, exhibiting higher anti-interference capabilities during optical readout. Therefore, research on AlScN-based opto-ferroelectric synaptic devices is of great significance for the design of advanced artificial intelligence devices. Summary of the Invention
[0005] Therefore, it is necessary to provide an AlScN-based optical-ferroelectric synaptic device and its fabrication method that addresses the shortcomings of existing technologies, enabling the application of AlScN materials with ferroelectric properties in artificial synaptic devices and further improving the performance of existing optical-ferroelectric synaptic devices.
[0006] To solve the above problems, this application adopts the following technical solution:
[0007] One of the objectives of this application is to provide an AlScN-based opto-ferroelectric synapse device, comprising a substrate, a bottom electrode, an AlScN ferroelectric layer, and a top electrode arranged sequentially from bottom to top. By applying an external voltage to the top electrode, the ferroelectric material inside the AlScN ferroelectric layer is polarized. After the external voltage is removed, the polarization direction of the AlScN ferroelectric layer is maintained, thereby realizing the writing and memorization of information.
[0008] In some embodiments, the substrate is a 00l oriented single-crystal sapphire or Si substrate.
[0009] In some embodiments, the bottom electrode comprises a metallic material or TiN or other n-type nitride material, wherein the metallic material comprises Pt, Mo, or W.
[0010] In some embodiments, when the bottom electrode is an n-type nitride, the opto-ferroelectric synapse device further includes a nitride nucleation layer and a nitride epitaxial layer grown sequentially on the substrate, wherein the n-type nitride is grown on the nitride epitaxial layer.
[0011] In some embodiments, the n-type nitride is GaN or AlGaN, and the material of the n-type nitride is a Si-doped n-type nitride with a carrier concentration of 10. 19 cm -3 Magnitude.
[0012] In some embodiments, when the bottom electrode is an n-type nitride, the opto-ferroelectric synaptic device further includes a metal electrode grown on the n-type nitride, wherein the metal electrode is made of Ti and Au and has a thickness of 10 nm or more.
[0013] In some embodiments, the Sc doping concentration in the AlScN ferroelectric layer ranges from 10% to 50%.
[0014] In some embodiments, the top electrode is made of Pt, Ti, or Au.
[0015] In some embodiments, the top electrode is circular with a diameter of less than 200 μm and a thickness of 10 nm.
[0016] The second objective of this application is to provide a method for fabricating the aforementioned AlScN-based opto-ferroelectric synaptic device, comprising the following steps:
[0017] The bottom electrode is grown on the substrate;
[0018] The AlScN ferroelectric layer is grown on the bottom electrode;
[0019] A photoresist mask pattern for the top electrode is prepared above the mesa of the AlScN ferroelectric layer, and then the top electrode is deposited by vapor deposition.
[0020] A photoresist mask pattern of a metal electrode is prepared in the exposed area of the bottom electrode, and then the bottom electrode is deposited by vapor deposition.
[0021] In some embodiments, the step of growing the bottom electrode on the substrate specifically includes the following steps: growing a metal or TiN bottom electrode layer on the substrate by magnetron sputtering or growing the bottom electrode by MOCVD.
[0022] In some embodiments, prior to the step of growing the bottom electrode on the substrate, the following step is further included: sequentially growing a nitride nucleation layer and a nitride epitaxial layer on the substrate using MOCVD.
[0023] In some embodiments, the step of growing the AlScN ferroelectric layer at the bottom electrode specifically includes the following steps:
[0024] An AlScN light-absorbing layer was grown on the bottom electrode using magnetron sputtering.
[0025] The AlScN light-absorbing layer is masked using photolithography, then the surface is etched using plasma etching, and finally the residual photoresist is removed using lift-off technology.
[0026] In some embodiments, the step of preparing a photoresist mask pattern for the top electrode above the AlScN ferroelectric layer mesa and then depositing the top electrode specifically includes the following steps: preparing a photoresist mask pattern for the top electrode above the AlScN ferroelectric layer mesa using photolithography, then depositing the top electrode, and finally using Lift Off technology to remove the photoresist in the photosensitive area of the detector and the top electrode material deposited on top of it.
[0027] In some embodiments, the step of preparing a photoresist mask pattern of a metal electrode in the exposed area of the bottom electrode and then depositing the bottom electrode specifically includes the following steps: preparing a photoresist mask pattern of a metal electrode in the exposed area of the bottom electrode by photolithography, then depositing the bottom electrode material by electron beam evaporation, and finally using LiftOff technology to remove the photoresist in the non-metal electrode area and the metal electrode material deposited on top of it.
[0028] In some embodiments, the solution used to remove the photoresist using the Lift Off technique is acetone.
[0029] The present application adopts the above technical solution, and its beneficial effects are as follows:
[0030] The photo-ferroelectric synaptic device and its fabrication method based on AlScN provided in this application include a substrate, a bottom electrode, an AlScN ferroelectric layer, and a top electrode arranged sequentially from bottom to top. Utilizing the characteristic that the polarization direction of AlScN material can be reversed with the direction of an external electric field, information is written via electrical pulses. The strong remanent polarization characteristic of AlScN material when the applied bias voltage is zero enables accurate information memorization. Taking advantage of its wide bandgap, lossless reading of information in the solar-blind ultraviolet band is achieved under zero bias voltage, and the fabrication method of the device structure at both ends is simple. Attached Figure Description
[0031] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the description of the embodiments of this application or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0032] Figure 1 This is a schematic diagram of the structure of the AlScN-based opto-ferroelectric synapse device provided in Embodiment 1 of this application.
[0033] Figure 2 This is a schematic diagram of another optical-ferroelectric synaptic device based on AlScN provided in Embodiment 1 of this application.
[0034] Figure 3 This is a schematic diagram illustrating the working principle of the AlScN-based opto-ferroelectric synaptic device provided in Embodiment 1.
[0035] Figure 4 This is a flowchart illustrating the steps of the fabrication method of the AlScN-based opto-ferroelectric synaptic device provided in Embodiment 2 of this application.
[0036] Wherein: 1-substrate; 2-bottom electrode; 3-AlScN ferroelectric layer; 4-top electrode; 2-1 nitride nucleation layer; 2-2 nitride epitaxial layer; 2-3 n-type nitride layer; 5 metal electrode forming an ohmic contact with the n-type nitride layer. Detailed Implementation
[0037] The embodiments of this application are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain this application, and should not be construed as limiting this application.
[0038] In the description of this application, it should be understood that the terms "upper", "lower", "horizontal", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application.
[0039] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, "multiple" means two or more, unless otherwise explicitly specified.
[0040] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments.
[0041] Example 1
[0042] Please see Figure 1 and Figure 2 This is a schematic diagram of an AlScN-based opto-ferroelectric synapse device provided in Embodiment 1, including a substrate 1, a bottom electrode 2, an AlScN ferroelectric layer 3, and a top electrode 4 arranged sequentially from bottom to top. The connection relationships of each component and their implementation methods are described in detail below.
[0043] In this embodiment, the substrate 1 is a 00l oriented single-crystal sapphire or Si substrate.
[0044] In this embodiment, the bottom electrode 2 comprises a metallic material or TiN or other n-type nitride material, wherein the metallic material comprises Pt, Mo or W.
[0045] In this embodiment, when the bottom electrode 2 is an n-type nitride, the opto-ferroelectric synapse device further includes a nitride nucleation layer 2-1 and a nitride epitaxial layer 2-2 grown sequentially on the substrate 1, and the n-type nitride 2-3 is grown on the nitride epitaxial layer 2-2.
[0046] It is understandable that the sequentially grown nitride nucleation layer and epitaxial layer can effectively reduce the defect density in n-type nitrides, laying the foundation for the subsequent growth of high-quality AlScN ferroelectric layers.
[0047] In this embodiment, the n-type nitride is GaN or AlGaN, and the material of the n-type nitride is a Si-doped n-type nitride with a carrier concentration of 10. 19 cm -3 Magnitude.
[0048] In this embodiment, when the bottom electrode 2 is an n-type nitride, the opto-ferroelectric synaptic device further includes a metal electrode grown on the n-type nitride to achieve ohmic contact. The metal electrode is made of Ti and Au and has a thickness of 10 nm or more.
[0049] In this embodiment, the Sc doping concentration in the AlScN ferroelectric layer 3 ranges from 10% to 50%.
[0050] In this embodiment, the top electrode 4 is made of metals such as Pt, Ti, and Au. The top electrode 4 is circular with a diameter of less than 200 μm and a thickness of 10 nm.
[0051] In this embodiment, the bottom electrode 5 is made of materials such as Ti and Au, and the thickness of the bottom electrode 5 is 10 nm or more.
[0052] Please see Figure 3 The working principle of the AlScN-based opto-ferroelectric synapse device provided in Embodiment 1 is explained as follows:
[0053] Figure 3 In (a), after applying a positive (negative) voltage exceeding the coercive field of AlScN to the top electrode 4, the ferroelectric polarization inside AlScN is directed downwards (P). down (Upward P) up After the external voltage is removed, due to the strong remanent polarization characteristics of AlScN ferroelectric material, the polarization direction can still be maintained under 0 bias voltage, thereby realizing the writing and memory of information. Figure 3 (b) Left-middle, downward ferroelectric remanent polarization P down An upward depolarization field E will be generated in AlScN. DP When exposed to ultraviolet light, photogenerated electrons will... DP Under the influence of the bottom electrode, photogenerated holes will move towards E. DP Under the influence of the current, the current moves towards the top electrode and can eventually detect a negative short-circuit current under zero bias. Figure 3 (b) Right center, upward ferroelectric remanent polarization P up A downward depolarization field E will be generated in AlScN. DP When exposed to ultraviolet light, photogenerated electrons will... DP Under the influence of the top electrode, photogenerated holes will move towards E. DP Under the influence of the photocurrent, the photocurrent moves towards the bottom electrode, and a positive short-circuit current can eventually be detected at zero bias. By detecting the direction of the photocurrent, lossless reading of the memory information can be achieved.
[0054] The photo-ferroelectric synapse device based on AlScN provided in Embodiment 1 of this application includes a substrate, a bottom electrode, an AlScN ferroelectric layer, and a top electrode arranged sequentially from bottom to top. It utilizes the characteristic that the polarization direction of AlScN material can be reversed with the direction of the external electric field to write information through electrical pulses; it utilizes the strong remanent polarization characteristic of AlScN material when the applied bias voltage is zero to achieve accurate information memory; and it utilizes its wide bandgap advantage to achieve lossless reading of information in the solar-blind ultraviolet band under zero bias voltage.
[0055] Example 2
[0056] Please see Figure 4 The flowchart below shows the steps of the fabrication method of the AlScN-based opto-ferroelectric synaptic device provided in Embodiment 2, including the following steps:
[0057] Step S110: Grow the bottom electrode on the substrate.
[0058] In some embodiments, the step of growing the bottom electrode on the substrate specifically includes the following steps: growing a metal or TiN bottom electrode layer on the substrate by magnetron sputtering or growing the bottom electrode by MOCVD.
[0059] In some embodiments, prior to the step of growing the bottom electrode on the substrate, the following step is further included: sequentially growing a nitride nucleation layer and a nitride epitaxial layer on the substrate using MOCVD.
[0060] Step S120: Grow the AlScN ferroelectric layer on the bottom electrode.
[0061] In some embodiments, the step of growing the AlScN ferroelectric layer on the bottom electrode specifically includes the following steps: growing an AlScN light-absorbing layer on the bottom electrode using magnetron sputtering; applying a photoresist mask to the AlScN light-absorbing layer using photolithography; etching the surface using plasma etching; and then removing the residual photoresist using lift-off technology.
[0062] In this embodiment, when growing the AlScN ferroelectric layer by magnetron sputtering, the magnetron sputtering process parameters are controlled as follows: the sputtering pressure is controlled at 0.7 Pa, the deposition temperature is 400 °C, the total flow rate of nitrogen and argon is 20 sccm, the doping concentration of Sc is adjusted by changing the sputtering power of Al target and Sc target, the Sc doping concentration range is 10% to 50%, and the AlScN deposition thickness is controlled at 100 nm.
[0063] Step S130: Prepare a photoresist mask pattern for the top electrode above the AlScN ferroelectric layer mesa, and then deposit the top electrode by vapor deposition.
[0064] In some embodiments, the step of preparing a photoresist mask pattern for the top electrode above the AlScN ferroelectric layer mesa and then depositing the top electrode specifically includes the following steps: preparing a photoresist mask pattern for the top electrode above the AlScN ferroelectric layer mesa using photolithography, then depositing the top electrode, and finally using Lift Off technology to remove the photoresist in the photosensitive area of the detector and the top electrode material deposited on top of it.
[0065] It is understood that in the photoresist mask pattern for preparing the top electrode on the AlScN ferroelectric layer mesa using photolithography, the selection of positive and negative photoresists depends on the design of the photomask pattern window. After development, the photoresist in the top electrode area on the AlScN ferroelectric layer mesa is retained, while the photoresist in the non-top electrode area is removed.
[0066] Step S140: Prepare a photoresist mask pattern of the metal electrode in the exposed area of the bottom electrode, and then deposit the bottom electrode by vapor deposition.
[0067] In some embodiments, the step of preparing a photoresist mask pattern of a metal electrode in the exposed area of the bottom electrode and then depositing the bottom electrode specifically includes the following steps: preparing a photoresist mask pattern of a metal electrode in the exposed area of the bottom electrode by photolithography, then depositing the bottom electrode material by electron beam evaporation, and finally using LiftOff technology to remove the photoresist in the non-metal electrode area and the metal electrode material deposited on top of it.
[0068] It is understood that in the photoresist mask pattern for preparing metal electrodes in the exposed area of the n-type nitride layer using photolithography, the selection of positive and negative photoresists depends on the design of the photomask pattern window. After development, the photoresist in the metal electrode pattern area is removed, while the photoresist in the non-metal electrode area is retained.
[0069] In some embodiments, the solution used to remove the photoresist using the Lift Off technique is acetone.
[0070] The fabrication method of the AlScN-based opto-ferroelectric synaptic device provided in Embodiment 2 of this application includes a substrate, a bottom electrode, an AlScN ferroelectric layer, and a top electrode arranged sequentially from bottom to top. Utilizing the characteristic that the polarization direction of AlScN material can be reversed with the direction of the external electric field, information is written via electrical pulses. Taking advantage of the strong remanent polarization characteristic of AlScN material when the applied bias voltage is zero, accurate information memorization is achieved. Furthermore, leveraging its wide bandgap advantage, lossless information reading in the solar-blind ultraviolet band is achieved under zero bias voltage, and the fabrication method of the device structure at both ends is simple.
[0071] It is understood that the technical features of the above embodiments can be combined arbitrarily. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.
[0072] The above are merely preferred embodiments of this application, and only specifically describe the technical principles of this application. These descriptions are only for explaining the principles of this application and should not be construed as limiting the scope of protection of this application in any way. Based on this explanation, any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application, as well as other specific embodiments of this application that can be conceived by those skilled in the art without creative effort, should be included within the scope of protection of this application.
Claims
1. A photo-ferroelectric synaptic device based on AlScN, characterized in that, The device includes a substrate, a bottom electrode, an AlScN ferroelectric layer, and a top electrode arranged sequentially from bottom to top. By applying an external voltage to the top electrode, the ferroelectric material inside the AlScN ferroelectric layer is polarized. After the external voltage is removed, the polarization direction of the AlScN ferroelectric layer is maintained, thereby enabling the writing and memorization of information. Ferroelectric remanent polarization generates a depolarization field in the AlScN ferroelectric layer with the opposite direction; the direction of the ferroelectric remanent polarization is consistent with the direction of the external voltage applied to the top electrode; When irradiated with ultraviolet light, photogenerated electrons move towards the bottom electrode or the top electrode in the opposite direction of the depolarization field, while photogenerated holes move in the same direction as the depolarization field. Finally, the corresponding negative or positive short-circuit current is detected under 0 bias voltage. By detecting the direction of the photocurrent, lossless reading of the memory information can be achieved.
2. The AlScN-based opto-ferroelectric synaptic device as described in claim 1, characterized in that, The substrate is a 00l oriented single-crystal sapphire or Si substrate.
3. The AlScN-based opto-ferroelectric synaptic device as described in claim 1, characterized in that, The bottom electrode comprises a metallic material or TiN or an n-type nitride, wherein the metallic material comprises Pt, Mo or W.
4. The AlScN-based opto-ferroelectric synapse device as described in claim 3, characterized in that, When the bottom electrode is an n-type nitride, the opto-ferroelectric synapse device further includes a nitride nucleation layer and a nitride epitaxial layer grown sequentially on the substrate, wherein the n-type nitride is grown on the nitride epitaxial layer.
5. The AlScN-based opto-ferroelectric synaptic device as described in claim 4, characterized in that, The n-type nitride is GaN or AlGaN, and is a Si-doped n-type nitride with a carrier concentration of 10. 19 cm -3 Magnitude.
6. The AlScN-based opto-ferroelectric synaptic device as described in claim 4, characterized in that, When the bottom electrode is the n-type nitride, the opto-ferroelectric synapse device further includes a metal electrode grown on the n-type nitride, wherein the metal electrode is made of Ti and Au and has a thickness of 10 nm or more.
7. The AlScN-based opto-ferroelectric synaptic device as described in claim 1, characterized in that, In the AlScN ferroelectric layer, the Sc doping concentration in the AlScN material ranges from 10% to 50%.
8. The AlScN-based opto-ferroelectric synaptic device as described in claim 1, characterized in that, The material of the top electrode is Pt, Ti, or Au.
9. The AlScN-based opto-ferroelectric synaptic device as described in claim 1 or 8, characterized in that, The top electrode is circular with a diameter of less than 200 μm and a thickness of 10 nm.
10. A method for fabricating an AlScN-based opto-ferroelectric synaptic device as described in claim 1, characterized in that, Includes the following steps: The bottom electrode is grown on the substrate; The AlScN ferroelectric layer is grown on the bottom electrode; A photoresist mask pattern for the top electrode is prepared above the mesa of the AlScN ferroelectric layer, and then the top electrode is deposited by vapor deposition. A photoresist mask pattern of a metal electrode is prepared in the exposed area of the bottom electrode, and then the bottom electrode is deposited by vapor deposition.
11. The method for fabricating the AlScN-based opto-ferroelectric synaptic device as described in claim 10, characterized in that, The step of growing the bottom electrode on the substrate specifically includes the following steps: growing a metal or TiN bottom electrode layer on the substrate by magnetron sputtering or growing the bottom electrode by MOCVD.
12. The method for fabricating the AlScN-based opto-ferroelectric synaptic device as described in claim 11, characterized in that, Before the step of growing the bottom electrode on the substrate, the method further includes the following step: sequentially growing a nitride nucleation layer and a nitride epitaxial layer on the substrate using MOCVD.
13. The method for fabricating the AlScN-based opto-ferroelectric synaptic device as described in claim 10, characterized in that, The step of growing the AlScN ferroelectric layer at the bottom electrode specifically includes the following steps: An AlScN light-absorbing layer was grown on the bottom electrode using magnetron sputtering. The AlScN light absorption layer is masked by photolithography, then the surface is etched by plasma etching, and finally the residual photoresist is removed by lift-off technology.
14. The method for fabricating the AlScN-based opto-ferroelectric synaptic device as described in claim 10, characterized in that, The step of preparing a photoresist mask pattern for the top electrode above the AlScN ferroelectric layer mesa and then depositing the top electrode specifically includes the following steps: preparing a photoresist mask pattern for the top electrode above the AlScN ferroelectric layer mesa using photolithography, then depositing the top electrode, and finally removing the photoresist in the photosensitive area of the detector and the top electrode material deposited on top of it using lift-off technology.
15. The method for fabricating an AlScN-based opto-ferroelectric synaptic device as described in claim 10, characterized in that, The step of preparing a photoresist mask pattern of a metal electrode in the exposed area of the bottom electrode and then depositing the bottom electrode specifically includes the following steps: preparing a photoresist mask pattern of a metal electrode in the exposed area of the bottom electrode by photolithography, then depositing the bottom electrode material by electron beam evaporation, and finally removing the photoresist in the non-metal electrode area and the metal electrode material deposited on top of it by lift-off technology.
16. The method for fabricating an AlScN-based opto-ferroelectric synaptic device as described in claim 13, 14, or 15, characterized in that, The solvent used to remove the photoresist using the Lift Off technique is acetone.