Multistage memory based on superlattice phase change material and preparation method thereof

Abstract

The invention belongs to the field of memories, and particularly discloses a multi-level memory based on a superlattice phase change material and a preparation method thereof, and the memory comprises a substrate, a waveguide layer, and a superlattice phase change material layer. The waveguide layer covers the substrate, the superlattice phase change material layer covers the substrate, and the superlattice phase change material layer is formed by periodically and alternately stacking two different phase change materials; the waveguide layer is used for receiving an incident light pulse and uniformly transmitting the energy of the light pulse to the superlattice phase change material layer; and the superlattice phase change material layer is used for controlling the ratio of a crystalline state to an amorphous state by utilizing the conversion between the crystalline state and the amorphous state through a thermo-optic effect according to the power and the pulse width of the optical pulse, and adjusting the projection rates under different powers and pulse widths. According to the invention, multi-level information storage can be realized, and the information capacity and the storage efficiency of the memory are improved.

Description

Technical Field

[0001] This application belongs to the field of memories, and more specifically, relates to a multi-level memory based on superlattice phase change materials and a preparation method thereof. Background Art

[0002] With the advent of the big data era, the amount of data has increased explosively, posing higher requirements for information storage technologies. Traditional semiconductor electrical storage technologies based on the von Neumann architecture face many challenges, such as the von Neumann bottleneck caused by the physical separation of the processor and memory units, the limitation of the electrical signal transmission on the computing speed, and the introduction of a large amount of energy loss. Traditional storage technologies are gradually reaching their physical limits and are difficult to meet the actual requirements for data storage in terms of security, reliability, energy efficiency, long lifespan, and low cost.

[0003] However, the storage capacity of existing memories is poor when facing massive data, and it is difficult to achieve multi-level storage. Summary of the Invention

[0004] Aiming at the defects of the existing technology, the purpose of this application is to provide a multi-level memory based on superlattice phase change materials and a preparation method thereof, aiming to solve the problem that the current memory has poor storage capacity and is difficult to achieve multi-level storage.

[0005] To achieve the above purpose, in a first aspect, this application provides a multi-level memory based on superlattice phase change materials, including: A substrate, a waveguide layer, and a superlattice phase change material layer; The waveguide layer covers the substrate, the superlattice phase change material layer covers the substrate, and the superlattice phase change material layer is formed by periodically and alternately stacking two different phase change materials; The waveguide layer is used to receive an incident light pulse and uniformly transfer the energy of the light pulse to the superlattice phase change material layer; The superlattice phase change material layer is used to convert between the crystalline state and the amorphous state according to the power and pulse width of the light pulse by using the thermo-optical effect to control the ratio of the crystalline state to the amorphous state, and adjust the transmittance under different powers and pulse widths to achieve multi-level information storage.

[0006] Optionally, the minimum number of repeating unit periods of the superlattice phase change material layer is at least 2, the total thickness is 12 nm - 24 nm, and the thickness of a single-layer phase change material is 2 nm - 8 nm.

[0007] Optionally, the superlattice phase change material layer includes germanium telluride and antimony telluride that are alternately stacked with each other, the single-layer thickness of germanium telluride is 4 nm - 8 nm, and the single-layer thickness of antimony telluride is 2 nm - 4 nm.

[0008] Optionally, it further includes an antioxidant layer, which covers the superlattice phase change material layer and is used to protect the superlattice phase change material layer from oxidation of the phase change material, so as to maintain the performance stability of the memory.

[0009] Optionally, the material of the antioxidant layer is indium tin oxide, and the thickness is 50nm - 200nm.

[0010] Optionally, the waveguide layer is a ridge waveguide, the material of the waveguide layer is silicon nitride, and the material of the substrate is silicon dioxide.

[0011] Optionally, the operating wavelength of the optical pulse is 1530nm - 1570nm; The power adjustment range of the optical pulse is 10mw - 30mw, and the pulse width adjustment range is 20ns - 100ns. By adjusting different powers and pulse widths, multiple distinguishable transmittance states can be achieved.

[0012] This application also provides a preparation method of a multi-level memory based on a superlattice phase change material, including: Providing a substrate; Preparing a silicon nitride ridge waveguide layer on the substrate through chemical vapor deposition, photolithography, and etching processes; Preparing a superlattice phase change material layer on the silicon nitride waveguide by using the thin film growth technology of molecular beam epitaxy; Covering an antioxidant layer on the superlattice phase change material layer by magnetron sputtering.

[0013] Optionally, the method for obtaining the silicon nitride ridge waveguide includes: Preparing a silicon nitride thin film on the substrate through chemical vapor deposition; Etching a waveguide structure on the silicon nitride thin film through electron beam exposure and inductively coupled plasma etching to obtain the silicon nitride ridge waveguide layer.

[0014] Optionally, it further includes: Removing redundant materials through electron beam exposure and inductively coupled plasma etching processes to complete overlay etching, and obtaining the prepared multi-level memory.

[0015] Generally speaking, compared with the prior art through the above technical solutions conceived by this application, the following beneficial effects are achieved: (1) Through the regulation of the crystalline and amorphous ratios of the superlattice phase change material layer in this application, combined with the adjustment of the power and pulse width of the optical pulse, multiple distinguishable transmittance states can be achieved, thereby realizing high-density multi-level information storage and significantly improving the information capacity and storage efficiency of the memory.

[0016] (2) The superlattice phase change material layer of this application is formed by periodically and alternately stacking two different phase change materials (such as germanium telluride and antimony telluride). The superlattice phase change material GeTe / has unique properties. Compared with the individual component materials, it has a higher crystallization temperature and good thermal stability; its thermal conductivity is lower, which can reduce power consumption. At the same time, near 1550 nm, the real part of the refractive index contrast between the crystalline state and the amorphous state of GeTe and is large, which is conducive to achieving an obvious transmittance change and improving the storage performance.

[0017] (3) The multi-level memory of this application can achieve multi-level storage by controlling the power and pulse width of the optical pulse. Compared with traditional storage technologies, it greatly improves the storage density and can meet the demand for massive data storage in the big data era.

[0018] (4) By covering an antioxidant layer on the superlattice phase change material layer, this application effectively prevents the oxidation of the phase change material and maintains the performance stability of the memory. The introduction of the antioxidant layer significantly extends the service life of the memory and reduces the maintenance and replacement costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 is one of the schematic structural diagrams of the multi-level memory based on the superlattice phase change material provided by the embodiment of this application; Figure 2 is the second schematic structural diagram of the multi-level memory based on the superlattice phase change material provided by the embodiment of this application; Figure 3 is the schematic diagram of the electric field distribution of the crystalline state and the amorphous state of GeTe / of this application; Figure 3 in which (a) represents the schematic diagram of the electric field in the crystalline state, Figure 3 in which (b) represents the schematic diagram of the electric field in the amorphous state; Figure 4 is the schematic diagram of the Poynting vector distribution of the crystalline state and the amorphous state of GeTe / of this application; Figure 4 in which (a) represents the schematic diagram of the Poynting vector in the crystalline state, Figure 4 in which (b) represents the schematic diagram of the Poynting vector in the amorphous state; Figure 5 is the schematic diagram of the optical absorption power distribution of the embodiment of this application; Figure 5 in which (a) represents the schematic diagram of the optical absorption rate in the crystalline state, Figure 5 in which (b) represents the schematic diagram of the optical absorption rate in the amorphous state; Figure 6 is the schematic diagram of the change of the temperature field distribution with time of the embodiment of this application; Figure 6 in which (a) represents the schematic diagram of the change of the temperature field at t = 10 ns,Figure 6 In Fig. (b), it shows a schematic diagram of the temperature field change at t = 20 ns, Figure 6 and in Fig. (c), it shows a schematic diagram of the temperature field change at t = 40 ns; Figure 7 It is a schematic diagram of the curve of the amorphous / crystalline ratio and the device transmittance changing with the time of the applied pulse in the embodiment of the present application; Figure 7 In Fig. (a), it shows a schematic diagram of the amorphous / crystalline ratio, Figure 7 and in Fig. (b), it shows a schematic diagram of the change in the device transmittance; Figure 8 It is a schematic diagram of the curve of the amorphous / crystalline ratio and the device transmittance changing with the applied pulse power in the embodiment of the present application; Figure 8 In Fig. (a), it shows a schematic diagram of the change in the amorphous / crystalline ratio with power, Figure 8 and in Fig. (b), it shows a schematic diagram of the change in transmittance with power; Figure 9 It is a schematic diagram of the process for preparing a multi-level memory based on a superlattice phase change material in the embodiment of the present application; In all the drawings, the same reference numerals are used to represent the same elements or structures, where: 1 is a substrate; 2 is a waveguide layer; 3 is a superlattice phase change material layer; 4 is an antioxidant layer. Detailed implementation manners

[0020] In order to make the objectives, technical solutions and advantages of the present application clearer, the present application will be further described in detail below with reference to the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0021] The term "and / or" in this article is a correlation relationship describing associated objects, indicating that there can be three relationships. For example, A and / or B can represent: A exists alone, A and B exist simultaneously, and B exists alone. The symbol " / " in this article represents an "or" relationship between associated objects. For example, A / B represents A or B.

[0022] The terms "first" and "second" etc. in the specification and claims of this article are used to distinguish different objects, rather than to describe a specific order of the objects. For example, the first response message and the second response message etc. are used to distinguish different response messages, rather than to describe the specific order of the response messages.

[0023] In the embodiments of the present application, words such as "exemplary" or "for example" are used to represent examples, illustrations or explanations. Any embodiment or design solution described as "exemplary" or "for example" in the embodiments of the present application should not be construed as being more preferred or having more advantages than other embodiments or design solutions. Rather, the use of words such as "exemplary" or "for example" is intended to present relevant concepts in a specific manner.

[0024] In the description of the embodiments of the present application, unless otherwise specified, the meaning of "a plurality of" refers to two or more. For example, a plurality of processing units refers to two or more processing units, etc.; a plurality of elements refers to two or more elements, etc.

[0025] The embodiments of the present application will be described below with reference to the accompanying drawings in the embodiments of the present application.

[0026] Refer to Figure 1 , the present application provides a multi-level memory based on a superlattice phase change material, including: a substrate 1, a waveguide layer 2, and a superlattice phase change material layer 3; The waveguide layer 2 covers the substrate 1, the superlattice phase change material layer 3 covers the substrate 1, and the superlattice phase change material layer 3 is formed by periodically and alternately stacking two different phase change materials; The waveguide layer 2 is used to receive an incident light pulse and uniformly transfer the energy of the light pulse to the superlattice phase change material layer 3; The superlattice phase change material layer 3 is used to control the ratio of the crystalline state to the amorphous state in the superlattice phase change material layer 3 according to the power and pulse width of the light pulse, and adjust the transmittance at different powers and pulse widths to achieve multi-level information storage; It further includes: an antioxidant layer 4, the antioxidant layer 4 covers the superlattice phase change material layer 3, and the antioxidant layer 4 is used to protect the superlattice phase change material layer 3 to prevent the phase change material from being oxidized, so as to maintain the performance stability of the memory.

[0027] Optionally, the minimum number of repetition unit periods of the superlattice phase change material layer is at least 2, the total thickness is 12 nm - 24 nm, and the thickness of a single-layer phase change material is 2 nm - 8 nm; The superlattice phase change material layer includes germanium telluride and antimony telluride that are alternately stacked with each other. The thickness of a single layer of germanium telluride is 4 nm - 8 nm, and the thickness of a single layer of antimony telluride is 2 nm - 4 nm; The material of the antioxidant layer is indium tin oxide, and the thickness is 50 nm - 200 nm; The waveguide layer is a ridge waveguide, the material of the waveguide layer is silicon nitride, and the material of the substrate is silicon dioxide; The operating wavelength of the optical pulse is 1530nm - 1570nm; The power adjustment range of the optical pulse is 10mw - 30mw, and the pulse width adjustment range is 20ns - 100ns. By adjusting different powers and pulse widths, multiple distinguishable transmittances can be achieved.

[0028] Specifically, the present application provides a multi-level memory based on a superlattice phase change material. By controlling the crystalline and amorphous ratios of the superlattice phase change material layer with optical pulses, multi-level information storage is realized. This memory includes a substrate, a waveguide layer, a superlattice phase change material layer, and an antioxidant layer, and has characteristics such as high-density storage, fast read and write, high stability, and low power consumption.

[0029] The memory structure and functions of the embodiments of the present application are described in detail below.

[0030] Substrate: Material: Silicon dioxide (SiO 2 )

[0031] Function: As the basic support layer of the entire memory, it provides stable mechanical and optical properties.

[0032] Waveguide layer: Material: Silicon nitride (Si 3 N 4 )

[0033] Structure: Ridge waveguide.

[0034] Function: Efficiently transmit the incident optical pulse to the superlattice phase change material layer.

[0035] It should be added that the silicon nitride ridge waveguide in the embodiments of the present application uses 2μm thick SiO 2 as the substrate to provide stable support. The top layer of silicon is 330nm thick, and the flat layer thickness is 165nm and the width reaches 1.3μm. This size design is conducive to the effective conduction and confinement of the optical field in the waveguide, ensuring the stable transmission of optical signals.

[0036] In the embodiments of the present application, by optimizing the waveguide structure, low-loss and high-stability transmission of the optical pulse energy is ensured.

[0037] Superlattice phase change material layer: Material: Two different phase change materials are periodically stacked alternately, such as germanium telluride (GeTe) and antimony telluride ( )

[0038] Structure parameter: The minimum number of repeating unit periods is at least 2.

[0039] The total thickness is 12nm - 24nm.

[0040] The thickness of the single-layer phase change material is 2 nm - 8 nm (the thickness of the GeTe single layer is 4 nm - 8 nm, and the thickness of the single layer is 2 nm - 4 nm).

[0041] Function: According to the power and pulse width of the optical pulse, regulate the ratio of the crystalline state to the amorphous state, and realize multi-level changes in the transmittance.

[0042] It should be added that the superlattice phase change material PCM1 / PCM2 in the embodiments of the present application: GeTe / is selected , and has 2 periods, with a total thickness of 12 nm, where the thickness of the single-layer GeTe is 4 nm, and the single-layer thickness is 2 nm. This size combination enables the superlattice phase change material to make full use of the thermo-optical effect under the action of an optical pulse, realize efficient conversion between the crystalline state and the amorphous state, and then change the transmittance of the device to complete the multi-level storage function.

[0043] Optionally, the working wavelength of the optical pulse is 1530 nm - 1570 nm. Optionally, for the superlattice phase change material GeTe / Near the working wavelength of 1550 nm, the real part of the refractive index contrast between the crystalline state and the amorphous state is large, and the crystallization temperature is relatively high and the thermal conductivity is relatively low.

[0044] The power adjustment range of the optical pulse is 10 mw - 30 mw, and the pulse width adjustment range is 20 ns - 100 ns. By adjusting the power and pulse width, multiple distinguishable transmittance states can be achieved.

[0045] Antioxidant layer: Material: Indium tin oxide (ITO).

[0046] Thickness: 50 nm - 200 nm.

[0047] Function: Covered on the superlattice phase change material layer to prevent the oxidation of the phase change material, maintain the performance stability of the memory, and improve the service life and reliability of the memory.

[0048] The multi-level memory in the embodiments of the present application mainly consists of a silicon nitride ridge waveguide and a superlattice phase change material GeTe / . The silicon nitride ridge waveguide uses 2-μm-thick SiO 2 as the substrate, with 330-nm-thick silicon added on the top layer, the thickness of the flat layer is 165 nm, and the width is 1.3 μm. On the basis of the silicon nitride waveguide, GeTe / with 2 periods and a total thickness of 12 nm is covered (4nm / 2nm) superlattice phase change material, and a layer of ITO material is covered to prevent the oxidation of the phase change material. The optical pulse is incident from one side of the device, and the evanescent wave couples the phase change material and the optical waveguide together, enabling the phase change material to absorb the energy of the optical field and undergo a phase change.

[0049] The following is the working principle of the memory in the embodiments of the present application, including the following parts: Optical pulse input: The optical pulse is transmitted through the waveguide layer to the superlattice phase change material layer.

[0050] Phase change regulation: According to the power and pulse width of the optical pulse, the ratio of the crystalline state to the amorphous state of the superlattice phase change material layer changes, resulting in multi-level changes in the transmittance.

[0051] Information storage: Different transmittance states correspond to different storage levels, realizing multi-level information storage.

[0052] The embodiments of the present application utilize the thermo-optic effect. By controlling the power and pulse width of the optical pulse, the phase change material is converted between the crystalline state and the amorphous state. When the optical pulse acts on the phase change material, the phase change material absorbs the energy of the optical field and the temperature rises. If the temperature exceeds the melting point, the crystalline GeTe / will turn into the amorphous state; if the temperature is maintained above the crystallization temperature and below the melting temperature for a period of time, the amorphous state will turn into the crystalline state. Since the optical properties of the crystalline and amorphous phase change materials are different, such as the refractive index and extinction coefficient are different, this will cause the transmittance of the device to change. By precisely controlling the optical pulse parameters and adjusting the crystalline / amorphous ratio of the phase change material, the multi-level storage function is realized. For example, when the power of the optical pulse is fixed, different pulse widths can make the device obtain different transmittances; when the pulse width is fixed and the power of the optical pulse is changed, the transmittance of the device can also change, and these transmittances have sufficient distinguishability to be used for encoding different information.

[0053] The following will elaborate on the memory regulation method in detail.

[0054] The regulation method of the memory in this embodiment is mainly based on the action of the optical pulse on the superlattice phase change material GeTe / to realize the regulation of the transmittance by changing the material state, and further achieve the purpose of multi-level storage.

[0055] 1. Principle of the action of the optical pulse: Utilizing the thermo-optic effect, the optical pulse becomes the key factor for regulation. When the optical pulse irradiates on the superlattice phase change material GeTe / the material will absorb the energy of the optical field, and the amount of absorbed energy depends on the power and pulse width of the optical pulse. The higher the power and the longer the pulse width, the more energy the material absorbs, and the more obvious the temperature rise. If the optical pulse makes the material temperature exceed the melting point, the originally crystalline GeTe / It will quickly transform into an amorphous state; when the light pulse keeps the material temperature above the crystallization temperature and below the melting temperature for a certain period of time, the amorphous material will gradually transform into a crystalline state.

[0056] 2. Phase change affects transmittance: GeTe / In the crystalline and amorphous states, there are significant differences in its optical properties. In the crystalline state, the real part of the refractive index of the material is larger, and the extinction coefficient is also larger, which makes its light absorption ability stronger and the transmitted light relatively less; in the amorphous state, on the contrary, the refractive index is lower, the extinction coefficient is small, the light absorption is less, the light loss is low, and the transmitted light is more. This difference in optical properties directly leads to the change of the device transmittance.

[0057] 3. Achieve multi-level storage: By precisely controlling the power and pulse width of the light pulse, the crystalline / amorphous ratio of GeTe / can be accurately adjusted. For example, when the power of the light pulse is fixed, changing the pulse width, as the pulse width increases, the light energy absorbed by the crystalline phase change material increases, the area transformed into the amorphous state exceeding the melting point increases, the amorphous ratio rises, and the device transmittance changes accordingly. Similarly, fixing the pulse width and increasing the power of the light pulse, the energy absorbed by crystalline GeTe / increases, more is transformed into the amorphous state, and the transmittance also changes. Different transmittance states correspond to different stored information, thus realizing the multi-level storage function and greatly improving the storage density and information processing ability of the memory.

[0058] The following will be a detailed description of the embodiments of the present application in combination with experimental simulation diagrams: Refer to Figure 3 , Figure 3 is a schematic diagram of the electric field distribution of crystalline and amorphous GeTe / ; it can be intuitively seen from the figure the differences in the electric field distribution in the two states. In the crystalline state, the electric field propagates in the form of waves and attenuates with the propagation distance, while in the amorphous state, the electric field distribution is uniform.

[0059] Refer to Figure 4 , Figure 4 is a schematic diagram of the Poynting vector distribution of crystalline and amorphous GeTe / , and it can be observed that the light absorption by the crystalline material causes the Poynting vector to decrease in the propagation direction, while there is no obvious attenuation in the amorphous state.

[0060] Refer to Figure 5 , Figure 5 is a schematic diagram of the light absorption power distribution. The figure respectively shows the light absorption power of the crystalline and amorphous phase change materials. In the crystalline state, the absorption power is large and attenuates with the propagation direction, while in the amorphous state, the absorption power is small and the attenuation is weak.

[0061] Refer to Figure 6 ,Figure 6 It is a schematic diagram of the temperature field distribution changing with time. In the figure, the temperature distribution of the cross-section of the superlattice phase change material at different time points under the action of an optical pulse with a peak power of 20 mW and a pulse width of 100 ns is presented. The temperature increases with time, and the distribution trend is consistent with the optical absorption power.

[0062] Refer to Figure 7 , Figure 7 It is a schematic diagram of the curves of the amorphous / crystalline ratio and the device transmittance changing with the time of the applied pulse. It can be seen from the figure that when the power of the optical pulse is fixed, as the pulse width increases, the relative changes in the amorphous ratio and the transmittance increase.

[0063] Refer to Figure 8 , Figure 8 It is a schematic diagram of the curves of the amorphous / crystalline ratio and the device transmittance changing with the power of the applied pulse. It can be seen from the figure that when the pulse width is fixed (100 ns), as the power increases, the amorphous ratio and the transmittance also increase, demonstrating that multi-level storage can be achieved by controlling the optical pulse parameters.

[0064] This application also provides a preparation method for a multi-level memory based on a superlattice phase change material, including: Providing a substrate; Preparing a silicon nitride ridge waveguide layer on the substrate through chemical vapor deposition, photolithography, and etching processes; Preparing a superlattice phase change material layer on the silicon nitride waveguide by using the thin film growth technology of molecular beam epitaxy; Covering an antioxidant layer on the superlattice phase change material layer by magnetron sputtering.

[0065] Optionally, the method for obtaining the silicon nitride ridge waveguide includes: Preparing a silicon nitride thin film on the substrate by chemical vapor deposition; Etching a waveguide structure on the silicon nitride thin film through electron beam exposure and inductively coupled plasma etching to obtain the silicon nitride ridge waveguide layer.

[0066] Optionally, it further includes: Removing excess materials through electron beam exposure and inductively coupled plasma etching processes to complete the overlay etching, and obtaining the prepared multi-level memory.

[0067] Specifically, the specific process of the preparation method in the embodiment of this application is as follows: S1. Providing a substrate Selecting silicon dioxide (SiO 2 ) as the substrate material.

[0068] S2. Preparing a silicon nitride ridge waveguide layer Chemical vapor deposition (CVD): Depositing a silicon nitride thin film on the substrate.

[0069] Lithography and etching: Through electron beam lithography and inductively coupled plasma etching (ICP) processes, a ridge waveguide structure is etched on the silicon nitride thin film.

[0070] S3. Prepare the superlattice phase change material layer Molecular beam epitaxy (MBE): Two phase change materials (such as GeTe and ) are alternately grown on the silicon nitride ridge waveguide to form a superlattice structure.

[0071] Parameter control: Ensure that the total thickness of the superlattice material layer is 12 nm - 24 nm, and the single-layer thickness is 2 nm - 8 nm.

[0072] S4. Cover the antioxidant layer Magnetron sputtering: Sputter indium tin oxide (ITO) thin film on the superlattice phase change material layer, with a thickness of 50 nm - 200 nm.

[0073] Process optimization: Ensure uniform coverage of the antioxidant layer to prevent oxidation of the phase change material.

[0074] S5. Complete the overlay Electron beam lithography and etching: Through electron beam lithography and inductively coupled plasma etching processes, remove the excess material to complete the overlay.

[0075] Final product: Obtain the prepared multi-level memory.

[0076] Refer to Figure 9 , Figure 9 is the complete process schematic diagram of the preparation method of the embodiment of the present application, including the following steps: 1) Prepare a layer of Si 2 N 3 film on the SiO 4 substrate by PECVD (plasma enhanced chemical vapor deposition); 2) Use an electron beam lithography device (EBL) to engrave the waveguide structure diagram on the electron beam resist, and then use inductively coupled plasma dry etching (ICP) to engrave the waveguide structure on the top silicon nitride, and remove the photoresist; 3) Grow a layer of SiO 2 dielectric around the silicon nitride by PECVD; 4) Wet-etch SiO 2 to expose the top of the Si 3 N 4 waveguide; 5) Grow a layer of phase change material around the silicon nitride waveguide ; 6) Then grow on Sb 2 Te 3Grow a layer of phase change material GeTe around the material; 7) Repeat operations 5 and 6; 8) Then deposit a layer of ITO around the GeTe material by magnetron sputtering; 9) Etch the excess material on SiO 2 to complete the overlay etching and remove the glue; It can be understood that the various numerical numbers involved in the embodiments of the present application are only for the convenience of description and are not used to limit the scope of the embodiments of the present application.

[0077] Those skilled in the art can easily understand that the above are only the preferred embodiments of the present application and are not intended to limit the present application. Any modifications, equivalent replacements, and improvements made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A multi-level memory based on superlattice phase change material, characterized in that: include: Substrate, waveguide layer, superlattice phase change material layer; The waveguide layer is covered on the substrate, the superlattice phase change material layer is covered on the substrate, and the superlattice phase change material layer is formed by periodically and alternately stacking two different phase change materials; The waveguide layer is used to receive incident light pulses and uniformly transfer the energy of the light pulses to the superlattice phase change material layer; The superlattice phase change material layer is used to control the ratio of crystalline state to amorphous state by converting between crystalline state and amorphous state according to the power and pulse width of the light pulse using the thermo-optical effect, and to adjust the projection rate under different power and pulse width to realize multi-level information storage.

2. The multi-level memory based on superlattice phase change material according to claim 1, characterized in that: The minimum number of repeating unit periods of the superlattice phase change material layer is at least 2, the total thickness is 12nm-24nm, and the thickness of a single layer of phase change material is 2nm-8nm.

3. The multi-level memory based on superlattice phase change material according to claim 2, characterized in that: The superlattice phase change material layer includes germanium telluride and antimony telluride alternately stacked with each other, the single layer thickness of the germanium telluride is 4nm-8nm, and the single layer thickness of the antimony telluride is 2nm-4nm.

4. The multi-level memory based on superlattice phase change material according to claim 1, characterized in that: It also includes an anti-oxidation layer, which covers the superlattice phase change material layer and is used to protect the superlattice phase change material layer and prevent the phase change material from being oxidized, so as to maintain the performance stability of the memory.

5. The multi-level memory based on superlattice phase change material according to claim 4, characterized in that: The material of the anti-oxidation layer is indium tin oxide, and the thickness is 50nm-200nm.

6. The multi-level memory based on superlattice phase change material according to claim 1, characterized in that: The waveguide layer is a ridge waveguide, the material of the waveguide layer is silicon nitride, and the material of the substrate is silicon dioxide.

7. The multi-level memory based on superlattice phase change material according to claim 1, characterized in that: The operating wavelength of the optical pulse is 1530nm-1570nm; The power adjustment range of the optical pulse is 10mw-30mw, and the pulse width adjustment range is 20ns-100ns. A variety of distinguishable transmittances can be achieved by adjusting different powers and pulse widths.

8. A method for preparing a multi-level memory based on superlattice phase change material, characterized in that: include: providing a substrate; A silicon nitride ridge waveguide layer is prepared on a substrate by chemical vapor deposition, photolithography and etching processes; The superlattice phase change material layer is prepared on the silicon nitride waveguide by using the thin film growth technology of molecular beam epitaxy; An anti-oxidation layer is coated on the superlattice phase change material layer by magnetron sputtering.

9. The preparation method according to claim 8, characterized in that: The method for obtaining the silicon nitride ridge waveguide comprises: preparing a silicon nitride thin film on a substrate by chemical vapor deposition; A waveguide structure is etched on the silicon nitride film by electron beam exposure and inductively coupled plasma etching to obtain the silicon nitride ridge waveguide layer.

10. The preparation method according to claim 9, characterized in that: Also includes: The redundant materials are removed by electron beam exposure and inductively coupled plasma etching process, and the overlay is completed to obtain a prepared multi-level memory.

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